Bees, Wasps and Ants
Hornets, Yellow Jackets, Paper Wasps. Being true social insects, these critters have a well-developed caste system. In a typical mature wasp nest there are many workers and one or more kings and queens. Unlike some of the other social insects discussed in this CD, there are fewer differences in the appearance of each caste.
Hornets, yellow jackets and paper wasps all exhibit the same general life cycle. Their nesting cycle is annual, with only mated queens surviving the winter in a variety of protected locations--including under bark and in attics. In early spring the queen emerges and may reoccupy an old nest, or construct a new one. Regardless of which condition prevails, the queen initially deposits a few single eggs-one to each cell. Upon hatching, the larvae are fed a variety of insect larvae (mainly caterpillars) that are captured and brought back to the nest by the adult queen wasp.
The adult wasps feed primarily on nectar, ripe fruit and other substances that are high in sugar. They do require a certain amount of protein in their diet which is typically acquired from the larvae. As adults wasps are feeding their larvae, the larvae exude a proteinaceous material from their mouth that is quickly consumed by the adult. The majority of these larvae will develop into adult workers, which take over the duties of expanding the nest, collecting food and feeding the young (Figure 18A). The queen continues to lay more eggs; this results in several generations with the colony continuing to increase in size into the fall. In the late fall, new kings and queens are produced, mating occurs, and the newly mated queens overwinter, completing the annual cycle.
Left. Mating yellow jackets. Right. Paper wasp.
Some consider these wasps beneficial, as they are predatory on different pest species. Besides feeding on caterpillars and other insects and spiders, these insects are attracted to any meat source, a phenomenon, which is frequently observed much to the displeasure of campers, clients of or participants in restaurants, snack bars and backyard barbecues
The nests of hornets, yellow jackets and paper wasps are constructed out of cellulose, which is collected by the adult workers from a variety of sources, including old newspapers, cardboard, weathered wood, and bark. Once collected, these materials are chewed, saliva is added and they are formed into cells basically appearing like those in honey bee comb.
With paper wasps the nest is a single layer that is suspended upside down by a short stalk. Around the home, paper wasp nests typically are found under eaves, along fences, or can be found attached to trees and plants. Hornet and yellow jacket nests may exist above or below ground; their nests are much larger than those of paper wasps, and are constructed of many layers of cells that are surrounded by a capsule-like structure.
Left. A paper wasp nest with a dozen or so workers. Right. A large hornet nest. Image courtesy CDC Healthwise Photo Library-Dr Gary Alpert.
Since paper wasp nest are single-layered it follows that mature colonies of these insects are much smaller than those of the multiplayer nests of hornets and yellow jackets. The nest of a paper wasp typically contains a few dozen adults while the nests of hornets and yellow jackets may number in the thousands.
Paper wasp colonies although common under the eaves of houses do not typically pose a threat to the homeowner unless the nest is disturbed. If disturbed they will readily defend the nest and sting is similar to that of a bee although unlike that of a honey bee these insects can sting repeatedly.
I was once asked in class how to remove a paper wasp nest from the eves of a home. Although not in the position to recommend such a task there are sprays available at garden centers that provide an instant knock down an subsequent kill of wasps and bees. One of the students in the class said she used hair spray which upon drying prevented the wasps from flying. Another student immediately added that she uses hair spray but lights it! Both seem quite unacceptable and possibly dangerous!
The most common social wasp found in the Western United States is the western yellow jacket. This species typically nests underground, but occasionally is found in wall voids and other protected locations. As with other members of this group these insects are predatory in nature but when their natural food is scarce they are attracted to any type of meat or sweets. Certain years these insects become extremely common and are major pests around campgrounds, restaurants and even backyards. One major factor relating to larger numbers during certain years is previous mild winters. Under these conditions the nests may not totally die out during the winter months.
An official from Catalina Island recently contacted me. The yellow jackets had become a major concern over the entire several-mile long island. In Avalon when customers ordered a hamburger and a coke at one of the restaurants it was a matter of whom or what got to the food first. One year on 3 separate occasions children had to Medi-vaced by helicopter out of the Boy Scout camps due to massive number of stings from these wasps.
Students frequently ask me what is the worst sting-bite that I personally have experienced. I have been stung by many scorpions, many species of ants, exotic caterpillars and hundreds of bees at one time and bitten by large beetles, giant waterbugs, assassin bugs, various tarantulas and black widows but the worst encounter was by a colony of yellow jackets. The sting of a yellow jacket or hornet is considerably worse than that of a honeybee. I was once called to remove a honeybee nest from a property. When I got there it was a yellow jacket nest in the ground. Even though, I was only prepared for honeybees (a veil and hat) I decided to continue. After about 15 stings (over a period of 20 minutes) I decided to retreat and get some better protective clothing. By the time I got back to my vehicle most of my body had turned bright red with hives and large red welts. Besides the initial pain I itched for several days. I once received a single sting from a large hornet in Mexico. The initial pain was much worse than that of a honeybee and within less than one minute I had such a severe headache that I could not stand up for several minutes.
Bald Face Hornet-Dolichovespula maculata. This is a North American insect commonly called the bald-faced hornet (or white-faced hornet or white-tailed hornet). Its well-known features include its hanging paper nests and the females' habit of defending them with repeated stings.
Bald Face Hornet. Image Courtesy of PiccoloNamek.
It belongs to a genus of wasps called yellow jackets in North America, but is not called that because it lacks yellow coloring. Instead, it is called a hornet in the American sense of a wasp that builds paper nests, especially one of the subfamily Vespinae. It is not a "true hornet" in the British sense, that is, a member of the genus Vespa in the same subfamily, such as the Asian giant hornet or the European hornet.
The bald-faced hornet lives throughout North America, including southern Canada, the Rocky Mountains, the western coast of the United States, and most of the eastern US. They are most common in the southeastern United States. They are best known for their large football-shaped paper nest, which they build in the spring for raising their young. These nests can sometimes reach 3 feet tall. Like the median wasp (Dolichovespula media) in Europe, bald-faced hornets are extremely protective of their nests and will sting repeatedly if disturbed.
Every year, queens that were born and fertilized at the end of the previous season begin a new colony. The queen selects a location for its nest, begins building it, lays a first batch of eggs and feeds this first group of larvae. These become workers and will assume the chore of expanding the nest — done by chewing up wood which is mixed with a starch in their saliva. This mixture is then spread with their mandibles and legs, drying into the paper-like substance that makes up the nest. The workers also guard the nest and feed on nectar, tree sap and fruit pulp. They also capture insects and arthropods, which are chewed up to be fed to the larvae. This continues through summer and into fall. Near the end of summer, or early in the fall, the queen begins to lay eggs which will become drones and new queens. After pupation, these fertile males and females will mate, setting up next year's cycle of growth.
Remains of Bald Faced Hornet Nest. Image Courtesy of Makuabob.
As winter approaches, the wasps die — except any just-fertilized queens. These hibernate underground, on hollow trees until spring or other protected locations. The nest itself is generally abandoned by winter, and will most likely not be reused. When spring arrives, the young queens emerge and the cycle begins again.
Bald-faced hornets visit flowers for nectar, especially in late summer, and can be minor pollinators.
Like other social wasps, bald-faced hornets have a caste system made up, in one nest, of the following: Queen — the fertile female which starts the colony and lays eggs; Workers — infertile females which do all work except laying eggs; Drones — males, which have no stingers, and are born from unfertilized eggs; New queens — fertile females, each of which, once fertilized, may start its own nest in the spring.
Bald-face hornets will sting repeatedly if disturbed. Like other stinging wasps, they can sting repeatedly because the stinger does not become stuck in the skin. Some suggest putting baking soda or meat tenderizer on the area of the sting, but others say such treatments do not work.
European Hornet-Vespa crabro. This species is commonly known simply as the "hornet", is the largest European true social wasp. The queen measures 21–1.4 inches long; males and workers are smaller. The antennae have 13 segments, while in females there are only 12
This species is not particularly aggressive except when defending the nest, and care must be taken when in its proximity, as the stings are quite painful. As with most stinging insects, European hornets will sting in self-defense when grabbed or stepped on.
Eyes are deeply indented, shaped like C. Wings are reddish-orange, the petiolate abdomen is brown striped with yellow. The European hornet is larger than common wasp, but smaller than some Asian hornet species. It has hair on the thorax and abdomen, although the European hornet is not so hairy as most bees.
European hornets are often mischaracterized as very aggressive and dangerous, and are greatly feared by some people. Some people believe that "three stings from the European hornet can kill an adult human, and that seven can kill a horse". These are common myths - a sting from a European hornet isn't any more dangerous than any other wasp sting, and European hornets are less aggressive than other wasps. In contrast, multiple Asian giant hornets stings are, in fact, more dangerous.
While impressive due to their size and loud sound, European hornets are in fact much less aggressive than some of their smaller relatives, such as the German wasp and the common wasp. When approached, European hornets can actually be seen to slowly crawl backwards and eventually flee, rather than attack. This can make it hard to remove hornets from indoors, if they happen to come in through an open window or door. While not aggressive when encountered far from the nest, multiple workers will vigorously defend the nest if provoked. Nests can be approached without provocation (by moving slowly and not breathing towards the nest) to about 20 inches. Nests are usually not a problem outside buildings, but because they drip feces, a bad smelling black liquid, nests inside sheds or walls can be a problem.
Unwarranted fear has often led to the destruction of nests, leading to the decline of the species, which is often locally threatened or even endangered. European hornets benefit from legal protection in some countries, notably Germany, where it has been illegal to kill a European hornet or nest since 1 January 1987, with a fine up to 50,000 Euros.
European hornets are attracted to lights at night, but are not attracted to human foods and food wastes. However, they can totally destroy fruits, such as apples, while the fruit is still on the tree. This is quite unlike the bald-faced hornet or other social wasps.
The Japanese Hornet. I have saved this beast for last since it is probably the most frightening of all the Hymenoptera. As its name implies it occurs mainly in Japan which is of course good for us since it is a treacherous and dangerous insect. It is quite large approaching the size of a thumb and by the way its sting, besides feeling like a hot nail driven into you, can also dissolve tissues of your thumb, actually any part of your body-ouch! Well it is gets worse. The sting-venom also contains an alarm pheromone that will incite mass attack from nearby hornets-hopefully not to a human. Unfortunately in many cases it is us as 40 to 70 people a year in Japan die from attack of these critters.
A Japanese Hornet.
As bad as this is for humans it is much worse for the European honeybee, Apis mellifera, the most common honeybee found around the world. These wasps will fly many miles looking for beehives to raid. They can fly as far as 60 miles in a day at 25 miles per hour. A searching hornet may actually follow a foraging bee back to its hive. Once finding the hive it attacks giving off the alarm pheromone attracting other hornet in the vicinity. Ultimately they typically attack in force with a relatively small but very effective army of 30 or more. You wouldn’t think such a small army would be that successful since a beehive can have upwards of 80,000 bees. However, one hornet can kill 40 bees a minute. Unfortunately honeybees possess relatively small stingers that are of minimal use in penetrating the thick exocutile of the invading hornets nor do they defend in mass. The hornets descend on the hive and systematically one by one cut the bees in half. In the interest of efficiency they typically cut off the defending bees heads. After a few hours the hive contains few if any adult bees but there are piles of heads, limbs and various other body parts. At that point the hornets gorge on the honey and rip the bee larvae (young) and pupae from their cells and carry them back to their nest to feed to their young.
However all is not totally lost. There is different species of honeybee which naturally occurs in Japan that has a defensive tactic it uses against these invaders. When a single hornet in search a beehive is detected, hundreds of the worker bees gather at the hive entrance but readily allow the hornet to enter. Once in the hive the bees immediately surround and totally cover the hornet with a ball-like mass of up to 500 individuals. They prevent the hornet from moving and begin to vibrate their wings muscles. This action produces heat raising the temperature in the center of the mass (where the hornet occurs) to around 117 F. This temperature is not lethal to the bees but the hornet cannot tolerate temperatures above 113 F and subsequently dies. Of course action prevents the “scout” hornet from releasing its pheromones which would normally attract other hornets in the vicinity to mass attack the hive.
In the mountains of Japan where these hornets are commonly encountered villagers eat them deep fried. Also a number of companies in Europe and Japan have begun to manufacture diet supplements and energy drinks which contain synthetic versions of secretions which the larval hornets feed to adults. The product sold as “hornet juice” is said to greatly enhance human endurance.
Parasitic (Parasitoids) Hymenoptera
There are many families of Hymenoptera that are parasitic. In strict entomological terms they are referred to as parasitoids. In the world of bugs parasite refers to an insect or one of its relatives (e.g. mites) that feeds on a host from a different groups animals (e.g. humans) but does not generally kill it in doing so. Example of this would include fleas, mites, lice and many others. A parasitoid is an insect or relative that typically lays its egg or eggs on or in its host which typically belong to the same group or animals (e.g. insect laying its eggs on another insect). Once the eggs hatch the larvae feed and develop internally or externally on that host and in doing so kill it.
Thread Waisted Wasps. As a group most thread waisted wasps are characterized by an elongated waist or petiole that joins the thorax to the abdomen. These are commonly found around the home. However some species have a narrow waist. In this case they can be separated from Vespidae by the front wing not bring folded longitudinally. These wasps can easily be distinguished from other similarly appearing wasps by the elongated stalk or petiole that connects the thorax to the abdomen; hence another common name is the thread-waisted wasps. The black and yellow mud dauber, Even though these are solitary insects a single nest may be composed of several elongated cylindrical cells made of mud and placed side by side until the make a mass about the size of a fist. The entire structure is then plastered over to make a smooth and even outer surface. Each inner cell is provided with several insect larvae or paralyzed spiders that the adult female has collected. A single egg is then deposited in each cell and the hatching wasp larvae complete their development on the provided prey. These wasps are much less aggressive than solitary forms, as they do not protect their nest. About the only way someone could be stung by one of these wasps is by accidentally stepping on or carelessly handling one, which seem very unlikely.
Black and Yellow Mud Dauber- Sceliphron caementarium. This is solitary insects that build nests out of mud in sheltered locations, frequently on man-made structures such as bridges, barns, open porches or under the eaves of houses. These nests are not aggressively defended, and stings are rare.
Black and Yellow Mud Dauber.
The black and yellow mud dauber's nest comprises a series of cylindrical cells that are plastered over to form a smooth nest that may attain nearly the size of a human fist. After building a cell, the female wasp captures several spiders. The captured prey are stung and paralyzed before being placed in the nest, and then a single egg is deposited on the prey within each cell. The wasp then seals the cell with mud. After finishing a series of cells, she leaves and does not return. Eventually, the hatching larva will eat the prey and emerge from the nest. A common species of cuckoo wasp, Chrysis angolensis, is frequently a cleptoparasite (steals they prey by laying its eggs on it)in Sceliphron nests, and is only one of many different insects that parasitize these mud daubers.
There are some 30 other species of Sceliphron that occur throughout the world, though in appearance and habits they are quite similar to S. caementarium. S. caementarium is widespread in Canada, the United States, Central America, South Africa and the West Indies, and has been introduced to many Pacific Islands (including Australia, Hawaii andJapan), Peru and Europe , where it has become established in the western Mediterranean Basin.
Organ Pipe Mud Dauber-Trypoxylon politum. These are fairly large wasps, shiny black with pale hind tarsi. Male organ pipe mud daubers are among the few male wasps of any species to stay at the nest. A male "stands guard" (to prevent theft of prey or nest materials, as well as to ward off parasites while a female is away collecting spiders. Mating typically occurs on her visits to the nest. They typically build their nests in sheltered locations, and large aggregations may form with dozens to hundreds of nests in a small area. The shape of their nest is the derivation of their common name.
Organ Pipe Mud Dauber, Nests and Parasitized Spiders M0ved from Nest. Images Courtesy or Pollinator.
Organ pipe mud daubers are also an exceedingly docile species of wasp, and generally pleasant to have around, as they serve to keep spider populations down. Stings to humans are very rare, bordering on non-existent, although if squeezed, they will sting in self-defense. There are a great many other species in the genus Trypoxylon (over 700 of them worldwide), mostly smaller in size and less abundant.
Sphecius speciosus-Cicada Killer. Cicada killer wasps are large, solitary wasps. The name may be applied to any species which uses cicadas as prey, though in North America it is typically applied to a single species, Sphecius speciosus, often simply referred to as "The cicada killer". However, since there are multiple species of related wasps, it is more appropriate to call it the Eastern pr Western cicada killers. These species occurs in the eastern, western and Midwest U.S. and southwards into Mexico and Central America. They are so named because they hunt cicadas and provision their nests with them. In North America they are sometimes called sand hornets, although they are not hornets, which belong to the family Vespidae.
Adult Eastern and Western cicada killer wasps are large, 1.5 to 5 cm (2/3 to 2 inches) long, robust wasps with hairy, reddish and black areas on the thorax (middle part), and are black to reddish brown marked with light yellow stripes on the abdominal (rear) segments. The wings are brownish. Coloration may superficially resemble that of yellow jackets or hornets. The females are somewhat larger than the males, and both are among the largest wasps seen in the Eastern United States, their unusual size giving them a uniquely fearsome appearance. European hornets (Vespa crabro) are often mistaken for Eastern cicada killers.
Solitary wasps (such as the Eastern cicada killer) are very different in their behavior from the social wasps such as hornets, yellow jackets, and paper wasps. Cicada killer females use their sting to paralyze their prey (cicadas) rather than to defend their nests. Adults feed on flower nectar and other plant sap exudates. Adults emerge in summer, typically beginning around late June or early July and continuing throughout the summer months. They are present in a given area for 60 to 75 days, until mid-September. The large females are commonly seen in mid-to-late summer skimming around lawns seeking good sites to dig burrows and searching shrubs and trees for cicadas.
The males are more often seen in groups, vigorously challenging one another for position on the breeding aggregation from which they emerged, and generally pursuing anything that moves or flies within close proximity. It is not unusual to see two or three male wasps locked together in midair combat, the aggregate adopting an erratic and uncontrolled flight path until one of the wasps breaks away. The male wasp's aggressive behavior is extremely similar to that of another robust insect of the area, the male carpenter bee. In both cases, while the males' vigorous territorial defense can be extremely frightening and intimidating to human passersby, the males pose no danger whatsoever. They will only grapple with other insects, and cannot sting.
This ground-burrowing wasp may be found in well-drained, sandy soils to loose clay in bare or grass-covered banks, berms and hills as well as next to raised sidewalks, driveways and patio slabs. Females may share a burrow, digging their own nest cells off the main tunnel. A burrow is 15 to 25 cm (6 - 10 in.) deep and about 3 cm (1.5 in.) wide. The female dislodges the soil with her jaws and pushes loose soil behind her as she backs out of the burrow using her hind legs, which are equipped with special spines that help her push the dirt behind her. The excess soil pushed out of the burrow forms a mound with a trench through it at the burrow entrance. Cicada killers may nest in planters, window boxes, and flower beds or under shrubs, ground cover, etc. Nests often are made in the full sun where vegetation is sparse.
Nest of Cicada Killer. Image Courtesy of Chuck Holliday.
After digging a nest chamber in the burrow, female cicada killers capture cicadas, paralyzing them with a sting; the cicadas then serve as food to rear their young. After paralyzing a cicada, the female wasp straddles it and takes off toward her burrow; this return flight to the burrow is difficult for the wasp because the cicada is often more than twice her weight. After putting the cicada in the nest cell, the female deposits an egg on the cicada and closes the cell with dirt. Male eggs are laid on a single cicada but female eggs are given two or sometimes three cicadas; this is because the female wasp is twice as large as the male and must have more food. New nest cells are dug as necessary off the main burrow tunnel and a single burrow may eventually have 10 to 20 cells. The egg hatches in one or two days, and the cicadas serve as food for the grub. The larvae complete their development in about 2 weeks. Overwintering occurs as a mature larva within an earth-coated cocoon. Pupation occurs in the nest cell in the spring and lasts 25 to 30 days. There is only one generation per year and no adults overwinter.
Although cicada killers are large, female cicada killer wasps are not aggressive and rarely sting unless they are grasped roughly, stepped upon with bare feet, or caught in clothing, etc. One author who has been stung indicates that, for him, the stings are not much more than a "pinprick". Males aggressively defend their perching areas on nesting sites against rival males but they have no sting. Although they appear to attack anything which moves near their territories, male cicada killers are actually investigating anything which might be a female cicada killer ready to mate. Such close inspection appears to many people to be an attack, but male and female cicada killers don't land on people and attempt to sting. If handled roughly females will sting, and males will jab with a sharp spine on the tip of their abdomen. Both sexes are well equipped to bite, as they have large jaws; however, they don't appear to grasp human skin and bite. They are non-aggressive towards humans and usually fly away when swatted at, instead of attacking. Cicada killers exert a natural control on cicada populations and thus may directly benefit the deciduous trees upon which their cicada prey feeds.
Chrysisid Wasps. These tiny wasps are characterized by their shining coloration made of iridescent blue, green, purple which are true pigments (red, brown and white) and are very rare in insects. The typical brilliance is emphasized by the exoskeleton sculpture, which is carved by a complex punctuation and by projections, crests and holes. In addition there is a reduction of the number of the external abdominal segments, the presence of 11 antennal segments and for the wing veins with 5 closed cells. Some tropical species have apterous females and a body without metallic reflections.
Cuckoo Wasps. Images Courtsey of (left) Pollinator and (right) Alvesgaspar.
Currently about 3,000 species have been described worldwide. Chrysidids are parasitoids with some species being cleptoparasites meaning they lay their eggs on host that are already parasitized by other wasps. In addition it is not uncommon for the newly hatched cleptoparasitic larvae to attack and kill the other parasitic larvae thus leaving more food for themselves
Velvet Ants. Their common name velvet ants refers to their dense hair which may be red, black, white, silver, or gold. They are known for their extremely painful sting, facetiously said to be strong enough to kill a cow, hence the common name cow killer or cow ant.
They invade the nests of wasps and bees as their exoskeleton is very tough and roughly textured to protect against stings. Like related families in the Vespoidea, males have wings but females are wingless. They exhibit extreme sexual dimorphism; the males and females are so different that it is almost impossible to associate the two sexes of a species unless they are captured while mating. In a few species the male is so much larger than the female that he carries her aloft while mating, a characteristic that is also seen in the closely related family Tiphiidae. In all Hymenoptera only the females sting because the stinger is a modified ovipositor. Like all wasps they can sting multiple times. A structure called a stridulitrum on the metasoma is used to produce a squeaking, chirping, or humming warning sound when handled.
Female (left) and Winged Male Velvet Ants.
Mature velvet ants feed on nectar. Although most species are strictly nocturnal, females some species are sometimes active up to two hours before sunset. It is thought they may not avoid light but rather are active during temperatures which usually occur only after sunset but on cool overcast days could occur earlier.
The male locates a female on the wing and mates. The female then enters an insect nest, typically a ground-nesting bee or wasp nest, and deposits eggs near the larvae or pupae. Her young develops as an ectoparasitoid, eventually killing and eating its immobile host. A few European species have been known to invade and raid bee or wasp nests.
Velvet ants occur worldwide, with some 5000 species, mainly in the tropics. They are especially common in desert and sandy areas, with most of the over 400 North American species found in the Southwestern United States and adjacent parts of Mexico, with others found in generally sandy regions throughout the United States and Canada; the same habitat where their hosts are most diverse.
Spider Wasps. These are one of the better know groups of large Hymenoptera. Most of the Spider Warps are orange and black, black and grey/white markings or just black, i.e., the very strong warning colors. They usually have tinted wings, smooth and shiny body. Their hind-legs are long and always have two prominent spurs. They tend to coil their antennae. Spider wasps are best distinguished from other similar wasps in having (in most species) a transverse groove dividing the mesopleuron (the mesepisternal sclerite, a region on the side of middle segment of the thorax above the point where the legs join) into halves.
Spider Wasp with Coiled Antennae and Mesoplural Transverse Groove Dividing Segment above Attachment of Second Pair of Legs
In South America spider wasp species may be referred to colloquially as marabunta or marimbondo, though these names can be generally applied to any very large stinging wasps). The family is cosmopolitan, with some 4,200 species in 4 subfamilies. All species are solitary, and most capture and paralyze prey, although some species are cleptoparasites of other pompilids, or ectoparasitoids of living spiders. Sexual dimorphism is not marked although females are often larger than the males.
Spider wasps are long-legged, solitary wasps that use a single spider as a host for feeding their larvae. They paralyze the spider with a venomous stinger. Once paralyzed, the spider is dragged to where a nest will be built – some wasps having already made a nest. A single egg is laid on the abdomen of the spider, and the nest – or burrow – is closed.
Spider Wasps Collecting Prey. Images Courtewy Tony Willis.
The size of the host can influence whether the wasp will lay an egg that will develop as a male, or an egg that will develop into a female – larger prey yielding the (larger) females. A complex set of adult behavior can then occur, such as spreading dirt or inspecting the area, leaving the nest site inconspicuous. When the wasp larva hatches it begins to feed on the still-living spider. After consuming the edible parts of the spider, the larva spins a silk cocoon and pupates – usually emerging as an adult the next summer. Some species lay the egg on a still-active spider, where it feeds externally on hemolymph (spider blood). In time, that spider will die, and the mature wasp larva will then pupate.
They usually hunt on ground with the characteristic wing flicking movement. The tarantula hawk is only one of a number of related species of wasps that mainly parasitize spiders and in entomological terms are referred to as parasitoids. They typically hunt out their prey, sting and paralyzed them and carry them back to their nest. The nest is typically a hole in the ground into which they insert one or more spiders upon which they subsequently lay a single egg. After hatching the wasp larva feed on the paralyzed prey until completing development.
Tarantula Hawk-Pepsis spp. This is a species of spider wasp which hunts tarantulas as food for it larvae. Up to two inches long with a blue-black body and bright rust-colored wings, tarantula hawks are among the largest of wasps. The coloring on their wings warns potential predators that they are dangerous (Aposematism). Their long legs have hooked claws for grappling with their victims. The stinger of a female tarantula hawk can be up to 1/3 inch long, and delivers a sting which is rated among the most painful in the insect world.
During the spiders’ reproductive season male tarantulas are usually emaciated from ignoring food while searching for females. The tarantula hawks thus prefer female tarantulas and seek them in their burrows. The females capture, sting, and paralyze the spider, Then they either drag the spider back into her own burrow or transport their prey to a specially prepared nest where a single egg is deposited on the spider’s body, and the entrance is covered. The wasp larva, upon hatching, begins to suck the juices from the still-living spider. After the larva grows a bit, it plunges into the spider's body and feeds voraciously, avoiding vital organs for as long as possible to keep it fresh. After completing pupation the adult wasp emerges from the nest. Tarantula wasps feed primarily on nectar and other natural sugary materials. The consumption of fermented fruit sometimes intoxicates them to the point that flight becomes difficult. While the wasps tend to be most active in daytime summer months, they avoid the very highest temperatures. The male tarantula hawk does not hunt; instead, it feeds off the flowers of milkweeds, western soapberry trees, or mesquite trees. The male tarantula hawk has a behavior called "hill-topping", where he sits atop tall plants and watches for females that are ready to reproduce.
Tarantula Hawk Dragging Prey to Nest and Feeding on Milkweed Nectar. Image Courtesy of Astrobradley (left) and Davehood (right).
The tarantula hawk is relatively docile and rarely stings without provocation. The sting, particularly of Pepsis formosa, is among the most painful of any insect, but the intense pain only lasts for about 3 minutes.[ Commenting on his own experience, one researcher described the pain as "…immediate, excruciating pain that simply shuts down one's ability to do anything, except, perhaps, scream. Mental discipline simply does not work in these situations”. In terms of scale, the wasp's sting is rated near the top of the Schmidt Sting Pain Index, second only to that of the bullet ant and is described by Schmidt as "blinding, fierce [and] shockingly electric". Because of their extremely large stingers, very few animals are able to eat them; one of the few animals that can is the roadrunner.
The U.S. State of New Mexico chose the insect in 1989 to become its official state insect. The selection of the insect was prompted by a group of Edgewood, New Mexico, elementary school children doing research on states which had adopted state insects. They selected three insects as candidates, and mailed ballots to all schools for a state wide election. The winner was the Tarantula Hawk Wasp (specifically, Pepsis formosa).
The RQ-16 T-Hawk unmanned aerial vehicle has been named after the Tarantula Hawk.
Gall Wasps-Cynipidae. These tiny wasps are also called gallflies with about 1300 species worldwide. As indicated they are generally very small creature (1-8 millimeters).
The reproduction of the gall wasp is partly pure two-sex propagation and partly pure parthenogenesis, in which a male is completely unnecessary. With most species, however, there is an alternation of generations with one two-sex generation and one parthenogenic generation annually.
The plant galls mostly develop directly after the female insect lays the eggs. The reason for gall formation is largely unknown but is a result of the present of the developing gall insect; it is speculated that chemical, mechanical and viruses triggers the process. The hatching larvae feed within the tissue of the galls and are also well-protected from external environmental effects. The host plants and the size and shape of the galls are specific to the majority of gall wasps with about 70% of the known species living in various types of oak trees. Galls occur on nearly all parts of trees including leaves, buds, branches, and roots. Other species of plant where galls are commonly found include eucalyptus, rose or maple trees, as well as many herbs. Frequently, identification a of species of gall forming insect is easier by the shape of the galls produced rather than the insect itself. Some of the more common types of galls caused by the feeding of these insects are discussed below.
Oak artichoke galls develop as a chemically induced distortion of leaf axillary or terminal buds on Pedunculate Oak (Quercus robur) or Sessile Oak (Quercus petraea) trees, caused by the parthenogenetic gall wasp Andricus fecundatrix which lays single eggs within leaf buds using their ovipositor. The larva lives inside a smaller hard casing inside the artichoke and this is released in autumn.
Oak Artichoke Galls. Image Courtesy Rasbak
The galls of the rose gall wasp (Diplolepis rosae) are also distinctive and are known as bedeguars or robin's pincushions. These are found on the shoots of dog roses and have a length of up to five centimeters with red long-haired outgrowths. Inside the galls are several chambers, which may be occupied by larvae.
Robin’s Pincushion on Rose. Image Courtesy of Bjorn Appel
Knopper galls develop as a chemically induced distortion of growing acorns on Pedunculate Oak (Quercus robur (L.)) trees, caused by gall wasps which lay eggs within buds using their ovipositor. The gall thus produced can greatly reduce the fecundity of the oak host, making the gall a potentially more serious threat than those which develop upon leaves, buds, and stems. The large one inch gall growth appears as a mass of green to yellowish-green, ridged, and at first sticky plant tissue on the bud of the oak, that breaks out as the gall between the cup and the acorn. If only a few grubs are developing within, then it may appear only as a group of bland folds. Where several grubs are competing for space the shape may become much more contorted, with several tightly bunched galls.
Kopper Galls. Image Courtesy of saharadesertfox.
Neuroterus numismalis is a gall wasp that forms chemically induced leaf galls on oak trees. It has both bisexual and agamic (parthenogenetic) generations and forms two distinct galls on oak leaves, the Silk button gall and Blister gall. The galls can be very numerous with more than a thousand per leaf. his Silk button spangle gall has a cover of golden hairs that give the impression of silk thread. The 0.3 cm button-shaped galls have a pronounced concavity and sit tightly against the leaf lamina.
Silk Button Galls on Oak. Image Courtesy of Image Courtesy of Beentree.
Neuroterus albipes is a gall wasp that forms chemically induced leaf galls on oak trees which has both bisexual and agamic generations and therefore forms two distinct galls, the Smooth Spangle gall and Schenck's gall. The normally cream colored saucer of the Smooth Spangle gall has a small cone elevated in its centre, a pronounced rim and they are sometimes found almost folded in two. The gall may have steaks of purple, red or other colors through it. Typically found on the lower surface, this gall is found more often on the upper surface than other spangle galls and although often grouped together, the numbers on each leaf are far fewer than in species such as Neuroterus quercusbaccarum. The gall is observed to swell appreciably once it has detached and fallen in late autumn. The gall has also been recorded as green, purple, red or pink.
Smooth Spangle Gall. Image Courtesy of Rosser1954
All bees collect nectar and pollen as their main source of food. One of the distinguishing characteristics of all these families is that their body hairs are profusely branched. This adaptation serves to capture and carry pollen. Worldwide, there are an estimated 20,000 species of bees (Michener, 2000), with approximately 4,000 species native to the United State. The non-native European honey bee (Apis mellifera) is the most important crop pollinator in the United States. However, because of disease and other factors the number of managed honey bee hives in the United States has declined by 50 percent since. During this same period, the amount of crop acreage requiring bee pollination has continued to grow. This makes native pollinators even more important to the future of agriculture.
Native bees provide free pollination services (as opposed to honey bee which are typically rented) and are often specialized for foraging on particular flowers, such as squash, berries or orchard crops. This specialization results in more efficient pollination and the production of larger and more abundant fruit from certain crops. The pollination done by native bees contributes an estimated $3 billion worth of crop production annually to the U.S. economy.
Native bees come in a wide range of colors and sizes, from tiny sweat bees less than a quarter of an inch long to bumble bees over an inch in length. Most are solitary, with each female creating and provisioning her nest without the support of a caste system of workers.
About 70 percent of native bees excavate underground nests while 30 percent of bees nest in wood tunnels, usually pre-existing holes such as those made by wood-boring beetles, but some will chew out the center of pithy twigs. In the case of both ground-nesting and wood-nesting bees, once the nest is complete, the mother bee generally dies. Her offspring will remain in the nest, passing through the egg, larva and pupa stages before emerging as an adult to renew the cycle. For some species this life cycle may progress over a matter of weeks, resulting in a second generation of bees in a single season. A few species may remain dormant for over a year. Most solitary bees however complete this life cycle over the course of a full year.
Native bees often only live for a few weeks as actively flying adults. They mate immediately upon emergence and the females begin nesting. They lay relatively few eggs compared to other insects, with a single female often laying less than 50 eggs before she dies. Male bees do not live long beyond mating, they do not collect pollen and have little value as pollinators.
While most of these wood-nesting and ground-nesting bees are solitary, some are gregarious, preferring to nest near others, a behavior that allows large aggregations to develop in favorable locations. Only a few tunnel and ground-nesting bee species ever develop truly social colonies, and often such behavior is environmentally dependent with some bees being social in one situation and being solitary in another. The one group of strictly social bees native to the United States is the group of approximately 45 bumble bee species.
The two habitat components need to be close enough together so that the bees can fly between them. The flight distance of a bee varies with the size of the bee. Small sweat bees and mining bees may not fly more than 200 or 300 yards from nest to forage area. Large bees (bumble bees, for example) can cross a mile or more of inhospitable, flower-less landscape to forage. But however large the bee, if it has to fly too far the effort begins to outweigh the benefits and the bee may either find somewhere else to nest or not survive in the landscape.
A third factor that influences habitat is insecticide exposure. To thrive, bees need minimal exposure to pesticides.
The Apidae are a large family of bees, comprising the common honey bees, stingless bees (which are also cultured for honey), carpenter bees, orchid bees, cuckoo bees, bumblebees, and various other less well-known groups. The family Apidae presently includes all the genera that were previously classified in the families Anthophoridae and Ctenoplectridae, and most of these are solitary species, though a few are also cleptoparasites. The four groups that were subfamilies in the old family Apidae are presently ranked as tribes within the subfamily Apinae. This trend has been taken to its extreme in a few recent classifications that place all the existing bee families together under the name "Apidae" (or, alternatively, the non-Linnaean clade "Anthophila"), but this is not a widely-accepted practice.
Stingless Bees. These can be found in most tropical or subtropical regions of the world, such as Australia, Africa, Southeast Asia, Central America and parts of Mexico and Brazil. The majority of native social bees of Central and South America are stingless bees, although only a few of them produce honey on a scale such that they are farmed by humans. They are also quite diverse in Africa and are farmed there also; meliponine honey is prized as a medicine in many African communities.
Being tropical, stingless bees are active all year round, although they are less active in cooler weather. Unlike other eusocial bees, they do not sting but will defend by biting if their nest is disturbed. In addition, a few have mandibular secretions that cause painful blisters. Despite their lack of a sting, stingless bees, being social, may have very large colonies made formidable by way of numerous defenders.
Stingless bees usually nest in hollow trunks, tree branches, underground cavities, or rock crevices but they have also been encountered in wall cavities, old rubbish bins, water meters, and storage drums. Many beekeepers keep the bees in their original log hive or transfer them to a wooden box, as this makes it easier to control the hive.
The bees store pollen and honey in large egg-shaped pots made of beeswax, typically mixed with various types of plant resin (sometimes called "propolis"). These pots are often arranged around a central set of horizontal brood combs, where the larval bees are raised. When the young worker bees emerge from their cells, they tend to remain inside the hive (much like honey bees, performing different jobs. As workers age, they become guards or foragers. Unlike the larvae of honey bees, stingless bee larvae are not fed directly by worker adults. The pollen and nectar are placed in a cell, an egg is laid, and the cell is sealed until the adult bee emerges after pupation ("mass provisioning"). At any one time, hives can contain anywhere from 300-80,000 workers, depending on species.
In a simplified sense, the sex of each bee depends on the number of chromosomes it receives. Female bees have two sets of chromosomes (diploid) - one set from the queen and another from one of the male bees or drones. Drones have only one set of chromosomes (haploid), and are the result of unfertilized eggs, though inbreeding can result in diploid drones.
Unlike true honey bees, whose female bees may become workers or queens strictly depending on what kind of food they receive as larvae (queens are fed royal jelly and workers are fed pollen), the caste system in meliponines is variable, and commonly based simply on the amount of pollen consumed; larger amounts of pollen yield queens in the genus Melipona. There is also a genetic component however, and as much as 25% (typically 5-14%) of the female brood may be queens. Queen cells in the former case can be distinguished from others by their larger size, as they are stocked with more pollen, but in the latter case the cells are identical to worker cells, and scattered among the worker brood. When the new queens emerge, they typically leave to mate, and most die. New nests are not established via swarms, but by a procession of workers who gradually construct a new nest at a secondary location. The nest is then joined by a newly-mated queen, at which point many workers take up permanent residence and help the new queen raise her own workers. If a ruling queen is herself weak or dying, then a new queen can replace her. For Plebeia quadripunctata, although less than 1% of female worker cells produce dwarf queens, they comprise six out of seven queen bees, and one out of five proceed to head colonies of their own. They are reproductively active but less fecund than large queens.
Myan Stingless Bees-Melipona beecheii and Meliopons. yucatanica, These are the only native bees cultured to any degree in the Americas. They were extensively cultured by the Maya for honey, and regarded as sacred. These bees are endangered due to massive deforestation, altered agricultural practices (especially insecticides), and changing beekeeping practices with the arrival of the Africanized honey bee, which produces much greater honey crops.
These bees have been kept by the lowland Maya for thousands of years. The traditional Mayan name for this bee is Xunan kab, literally meaning "royal lady". The bees were once the subject of religious ceremonies and were a symbol of the bee-god Ah-Muzen-Cab, who is known from the Madrid Codex.
The bees were, and still are, treated as pets. Families would have one or many log-hives hanging in and around their house. Although they are stingless, the bees do bite and can leave welts similar to a mosquito bite. The traditional way to gather bees, still favored amongst the locals, is to find a wild hive; then the branch is cut around the hive to create a portable log, enclosing the colony (Figure 37). This log is then capped on both ends with another piece of wood or pottery and sealed with mud. This clever method keeps the melipine bees from mixing their brood, pollen, and honey in the same comb as the European bees. The brood is kept in the middle of the hive, and the honey is stored in vertical "pots" on the outer edges of the hive. A temporary, replaceable cap at the end of the log allows for easy access to the honey while doing minimal damage to the hive. However, inexperienced handlers can still do irreversible damage to a hive, causing the hive to swarm and abscond from the log. On the other hand, with proper maintenance, hives have been recorded as lasting over 80 years, being passed down through generations. In the archaeological record of Mesoamerica, stone discs have been found which are generally considered to be the caps of long-disintegrated logs which once housed the beehives.
Traditional Stingless Bee Hive. Image Courtesy of en.wikipedia.org/wiki/Image:Belize37.jpg
Balché, an alcohol beverage similar to mead, was made from fermented honey and the bark of the leguminous Balché tree (Lonchocarpus violaceus), hence its name. It was traditionally brewed in a canoe. The drink was known to have entheogenic properties, that is, to produce mystical experiences, and was consumed in medicinal and ritual practices. The hallucinogenic properties come from tan alkaloid in the bark of the Balché tree, although whether the hallucinogens came from the bark or the honey, which beekeepers would harvest after placing the nests near the trees, remains uncertain. Toxic and hallucinogenic substances can be found in all honey, if bees collect nectar and pollen from certain types of vegetation. Most likely, it is a combination of the two, since balché is made from both the Melipona honey gathered from the Balché flowers, and from the bark of the tree, brewed and fermented together.
Lost-wax casting, a common metalworking method which is typically found where the inhabitants keep bees, was also utilized by the Maya. The wax from Melipona is soft and easy to work, especially in the humid Mayan lowland. This allowed the Maya to create smaller works of art and jewelry that would be difficult to forge. It also makes use of the leftovers from honey extraction. If the hive was damaged beyond repair, the whole of the comb could be used, thus using the entire hive. With experienced keepers, though, only the honey pot could be removed, the honey extracted, and the wax used for casting or other purposes.
The outlook for meliponines in Mesoamerica is grim. The number of active Melipona beekeepers is rapidly declining in favor of the more economical, non-indigenous Africanized Apis mellifera. The high honey yield, 100 kilograms or more annually, along with the ease of hive care and ability to create new hives from existing stock, commonly outweighs the negative consequences of "killer bee" hive maintenance. Furthermore, there are flora that the Africanized honey bees do not visit, such as those in the tomato family, and several forest trees and shrubs, which rely on the native stingless bees for pollination. There has already been a decline in populations of native flora in areas where stingless bees have been displaced by Africanized honey bees. An additional blow to the art of meliponine beekeeping is that many of the meliponine beekeepers are now elderly men and women, whose hives may not be cared for once they die. The hives are considered similar to an old family collection, to be parted out once the collector dies or to be buried in whole or part along with the beekeeper upon death. In fact, a survey of a once-popular area of the Mayan lowlands shows the rapid decline of beekeepers, down to around 70 in 2004 from thousands in the late 1980s. It is traditional in the Mayan lowlands that the hive itself or parts of the hive be buried along with the beekeeper to volar al cielo, "to fly to heaven". There are conservation efforts underway in several parts of Mesoamerica.
South American Stingless Bee-Trigona spinipes. This is a species of stingless bee occurring in South America where it is called arapuá, irapuá or abelha-cachorro ("dog-bee") (Figure 38.). The species name means "spiny feet" in Latin. Trigona spinipes builds its nest on trees (or on buildings and other human structures), out of mud, resin, wax, and assorted debris, including dung. Therefore, its honey is not especially fit for consumption, even though it is reputed to be of good quality by itself, and is used in folk medicine. Colonies may have from 5000 to over 100 000 workers.
Adult and Nest of South American Stingless Bees. Images Courtesy of Reynaldo and (Left) Jorge Stolfi
This species will attack in swarms when they feel the nest is threatened. They cannot sting, and their bite is not very effective but quite annoying. Their main weapon against predatory animals (including people) is to get themselves entangled in the victim's hair and buzz loudly. These bees uses odor trails, sometimes extending to several hundred yards in order lead nest mates from the hive to a food source. Moreover they will frequently follow trail similar chemicals used by other bee (such as carpenter bees, Africanized honeybees and other stingless bees) for the same purpose, frequently killing or driving them away and taking over their food source.
This bee has been considered an agricultural pest for some cultures, such as passion fruit, because it damages leaves and flowers while collecting nest materials, and tunnels through the unopened flowers to collect the nectar (thus frustrating their normal pollinators).[ On the other hand, they are significant pollinators on their own, e.g. for onions.
Attack by stingless bee although not considered dangerous to humans can be very annoying if not scary, especially if the victim is not expecting it. On one occasion Pat (my wife) and I were collecting insects in Monte Verde Costa Rica. Without any warning there were hundreds of bees on us. As indicated above they got into our clothing and hair. As indicated their bite was not especially painful but when hundreds of bees are biting you especially around the face neck and other areas of the face it can be disconcerting to say the least. She still talks about it today (30 years ago).
Carpenter Bees. Carpenter bees are large, hairy bees with over 500 species distributed worldwide. Their name comes from the fact that nearly all species build their nests in burrows in dead wood, bamboo, or structural timbers.
In the United States, there are two eastern species, Xylocopa virginica, and Xylocopa micans, and three other species that are primarily western in distribution, Xylocopa varipuncta, Xylocopa tabaniformis orpifex and Xylocopa californica. X. virginica is by far the more widely distributed species. Some are often mistaken for a bumblebee species, as they can be similar in size and coloration, though most carpenter bees have a shiny abdomen, while in bumblebees the abdomen is completely clothed with dense hair. Males of some species have a white or yellow face, where the females do not; males also often have much larger eyes than the females, which relates to their mating behavior. Male bees are often seen hovering near nests, and will approach nearby animals. However, males are harmless since they do not have a stinger. Female carpenter bees are capable of stinging, but they are docile and rarely sting unless caught in the hand or otherwise directly provoked.
Many Old World carpenter bees have a special pouch-like structure on the inside of their thorax called the acarinarium where certain species of mites (Dinogamasus spp.) reside. The exact nature of the relationship is not fully understood, though in other bees that carry mites where the mites are beneficial, feeding either on fungi in the nest, or on other, harmful mites.
Carpenter bees are traditionally considered solitary bees, though some species have simple social nests in which mothers and daughters may cohabit. However, even solitary species tend to be gregarious. There are two very different mating systems that appear to be common in carpenter bees, and often this can be determined simply by examining specimens of the males of any given species. Species in which the males have large eyes are characterized by a mating system where the males either search for females by patrolling, or by hovering and waiting for passing females, whom they then pursue. In the other type of mating system, the males often have very small heads, but there is a large, hypertrophied glandular reservoir in the mesosoma, which releases pheromones into the airstream behind the male while it flies or hovers. The pheromone advertises the presence of the male to females.[
These bees come in a variety of sizes although most are slightly larger than a honey bee. One of the most common species is the valley carpenter bee that is characterized by solid black females and golden males. They are as large as or larger than bumblebees.
Female and Male Valley Carpenter Bees.
As previous indicated these bees nest in wood. Their colonies consist of a series of tunnel-shaped burrows. As do other bees, carpenter bees collect pollen to feed to their young. Once collected, the pollen is formed into a ball about the size of a small marble. A single egg is then deposited on each ball, which subsequently is compartmentalized within the burrows (Figure 40). Their life cycle is completed in a few months as the larvae develop on the pollen balls.
A Tunnel of a Carpenter Bee with Developing Larva and Pupa. Image Courtesy Univar Corporation.
Carpenter bees are not true social insects as there is no division of labor, but many bees may occupy the same nesting burrow. The burrows typically are used year after year and can become rather extensive. Even though these are wood infesting insects, rarely do they do any significant damage to homes.
Occasionally they can be bothersome to the homeowner because the males are especially aggressive and will fly up to and buzz in a person’s face; however, they are totally harmless, as male Hymenoptera do not have stingers. The sting of the female is quite painful, but she is much less aggressive.
In the telephone industry these bees are referred to as pole bees because they frequently nests in telephone poles. Even though they typically do not sting, they buzz linemen and in some cases this has resulted in injuries as a result of the workers’ attempts to avoid their harassment. I am aware of more than one case where linemen have fallen from poles due to “bee attack”.
Bumble Bees. A bumblebee (or bumble bee) is any member of the bee genus Bombus, in the family Apidae. There are over 250 known species, existing primarily in the Northern Hemisphere although they are common in New Zealand and Tasmania.
Bumblebees are social insects that are characterized by black and yellow body hairs, often in bands. However, some species have orange or red on their bodies, or may be entirely black (Figure 41). Another obvious (but not unique) characteristic is the soft nature of the hair (long, branched setae), called pile, that covers their entire body, making them appear and feel fuzzy. They are best distinguished from similarly large, fuzzy bees by the form of the female hind leg, which is modified to form a shiny concave surface that is bare, but surrounded by a fringe of hairs used to transport pollen (in similar bees, the hind leg is completely hairy, and pollen grains are wedged into the hairs for transport). Like their relatives the honey bees, bumblebees feed on nectar and gather pollen to feed their young. One characteristic of bees in general is that the body hairs are profusely branched making them more efficient in trapping pollen. Their mouthparts consist of a tube-like proboscis for siphoning the nectar from pants. It is coiled up when not in use.
A Bumbles Bee with Uncoiled Proboscis in Preparation for Removal of Nectar. Image Courtesy FFubs. Right. Bumblebee with Pollen Trapped on Hairs. Image Courtesy of Jesse Hickman
The brightly-colored pile of the bumble bee is a form of aposematic signal, meaning the bright coloration is a sign that I am bad-don’t mess with me (Figure 42). Depending on the species these colors can range from entirely black, to bright yellow, red, orange, white, and pink. Thick pile can also act as insulation to keep the bee warm in cold weather. Further, when flying a bee builds up an electrostatic charge, and as flowers are usually well grounded, pollen is attracted to the bee's pile when it lands. When a pollen covered bee enters a flower, the charged pollen is preferentially attracted to the stigma (female part of plant-thus fertilization occurs) because it is better grounded than the other parts of the flower.
Brightly Colored Bumble Bee. Image Courtesy Christian Sand.
Bumblebees are typically found in higher latitudes and or high altitudes; though exceptions exist (there are a few lowland tropical species). A few species range into very cold climates where other bees might not be found; Bombus. polaris can be found in northern Ellesmere Island (west of Greenland)—the northern most occurrence of any true social insect. One reason for this is that bumblebees can regulate their body temperature, via solar radiation, internal mechanisms of "shivering" and cooling from the abdomen (called heterothermy).
Bumblebee colonies are usually much less extensive than those of honey bees. This is due to a number of factors including: the small physical size of the nest cavity, a single female is responsible for the initial construction and reproduction that happens within the nest, and the restriction of the colony to a single season (in most species). Often, mature bumblebee nests will hold fewer than 50 individuals and are typically found below ground (Figure 43). They sometimes construct a wax canopy over the top of their nest for protection from moisture and insulation. Bumblebees do not often preserve their nests through the winter, though some tropical species live in their nests for several years (and their colonies can grow quite large, depending on the size of the nest cavity). In temperate species, the last generation of summer includes a number of queens who overwinter separately in protected spots.
Bumblebees Nest in a Shed. Image Courtesy Pete Griggs.
Bumblebee nests are first constructed by over-wintered queens in the spring. Upon emerging from hibernation, the queen collects pollen and nectar from flowers and searches for a suitable nest site. The characteristics of the nest site vary among species, with some preferring to nest in underground holes and others in tussock grass or directly on the ground. Once the queen has found a site, she prepares wax pots to store food and wax cells into which eggs are laid. These eggs then hatch into larvae, which cause the wax cells to expand into a clump of brood cells.
These larvae need to be fed both nectar for carbohydrates and protein in order to develop. Bumblebees feed nectar to the larvae by chewing a small hole in the brood cell into which nectar is regurgitated. Larvae are fed pollen in one of two ways, depending on the species. So called "pocket-maker" bumblebees create pockets of pollen at the base of the brood cell clump from which the larvae can feed themselves. Conversely, "pollen-storers" store pollen in separate wax pots and feed it to the larvae in the same fashion as nectar. Bumble bees are incapable of trophallaxis (direct transfer of food from one bee to another) which is common in other hymenoptera such as ants.
After the emergence of the first or second group of workers, workers take over the task of foraging and the queen spends most of her time laying eggs and caring for larvae. The colony grows progressively larger and at some point will begin to produce males and new queens. The point at which this occurs varies among species and is heavily dependent on resource availability and environmental factors. Unlike the workers of more advanced social insects, bumblebee workers are not physically reproductively sterile and are able to lay haploid eggs that develop into viable male bumble bees. Only fertilized queens can lay diploid eggs that mature into workers and new queens.
Early in the colony cycle, the queen bumblebee compensates for potential reproductive competition from workers by suppressing their egg-laying by way of physical aggression and pheromonal signals. Thus, the queen will usually be the mother of all of the first males laid. Workers eventually begin to lay males later in the season when the queen's ability to suppress their reproduction diminishes. The reproductive competition between workers and the queen is one reason that bumble bees are considered "primitively social insects".
New queens and males leave the colony after maturation. Males in particular are forcibly driven out by the workers. Away from the colony, the new queens and males live off nectar and pollen and spend the night on flowers or in holes. The queens are eventually mated (often more than once) and search for a suitable location for diapause (dormancy). The following season they will form new colonies.
Bumblebees generally visit flowers exhibiting the bee pollination syndrome. They can visit patches of flowers up to 1-2 kilometers from their colony. Bumblebees will also tend to visit the same patches of flowers every day, as long as nectar and pollen continue to be available. While foraging, bumblebees can reach ground speeds of up to 15 m/s (54 km/h).
When bumblebees arrive at a flower, they extract nectar using their long tongue. Many species of bumblebee also exhibit what is known as "nectar robbing": instead of inserting the mouthparts into the flower normally, these bees bite directly through the base of the flower to extract nectar, avoiding pollen transfer. These bees obtain pollen from other species of flowers that they “legitimately” visit.
Pollen is removed from flowers deliberately or incidentally by bumblebees. Incidental removal occurs when bumblebees come in contact with the anthers of a flower while collecting nectar. The bumblebee's body hairs receive a dusting of pollen from the anthers which is then groomed into the pollen baskets.
Bumblebees are also capable of pollination. With certain species of plants it I difficult to remove the pollen from the anthers. In order to release the pollen, bumblebees and some species of solitary bees are able to grab onto the flower and move their flight muscles rapidly, causing the flower and anthers to vibrate, dislodging pollen. This resonant vibration is called buzz pollination. The honeybee rarely performs buzz pollination. About 8% of the flowers of the world are primarily pollinated using buzz pollination. This behavior is very important for some plants such as blueberries, cranberries, tomatoes and peppers, all of which release pollen from pores within the anthers (similar to salt being shaken from a salt shaker).
In at least a few species, once a bumblebee has visited a flower, it leaves a scent mark on the flower. This scent mark deters visitation of the flower by other bumblebees until the scent degrades wears off. It has been shown that this scent mark is a general chemical bouquet that bumblebees leave behind in different locations (e.g. nest, neutral, and food sites) and they learn to use this bouquet to identify both rewarding and unrewarding flowers. In addition, bumblebees rely on this chemical bouquet more when the flower has a high handling time (i.e. it takes a longer time for the bee to find the nectar).
Once they have collected nectar and pollen, bumblebees return to the nest and deposit the harvested nectar and pollen into brood cells, or into wax cells for storage. Unlike honey bees, bumblebees only store a few days' worth of food and so are much more vulnerable to food shortages.
Providing Nest Locations for Bumble Bees. Unlike solitary bees, which can be very particular about tunnel diameters, bumble bees are flexible in their nesting needs. All they want is a warm, dry cavity, roughly the size of a shoebox (Figure 44). Artificial nests can be constructed to attract bumble bees, but occupancy is typically extremely low – often far less than 25 percent.
A simple wooden bumble bee box can be made from preservative-free lumber. An appropriate size will have internal dimensions of about 7 inches high by 7 inches wide and 7 inches long. Drill a few ventilation holes on the upper sides of the box (near the roof) and cover with window screen to deter ants. Also drill some drainage holes in the bottom. Make an entrance tunnel from 3/4-inch diameter plastic pipe and fill the box with soft bedding material, such as short lengths of soft unraveled string, dry straw or upholsterer's cotton (do not use cotton balls, as the fibers become tangled in the bees' legs). The box must be weather tight; if the nest gets damp, the larvae may become too cold and mold and fungus will grow.
Bumble Bee Box.
Place the nest in a dry, undisturbed area that has some obvious landmarks (a fence post, rock or building) to aid bee navigation; these landmarks are important to bees returning from foraging. Nesting boxes that are at ground level or slightly buried (either with soil or straw) are the most attractive to queens of many species. Boxes placed on the surface should be level and stable. If you are burying your box, extend the entrance pipe so it gently slopes up to the surface and clear the vegetation from an area a few inches around where the pipe surfaces.
The best time to install a bumble bee nest box is in early spring, when the first queens have emerged from hibernation and are searching for a nest site; in many areas, this is when the willows first start blooming.
Bumble bee nests require little maintenance. Watch your boxes through the spring and early summer. Any above-ground boxes that are unoccupied by late July can be removed, cleaned and put into storage until the following spring. This is not vital, and if you have a lot of boxes on a large site it may not be practical. In late fall or early winter inspect all the boxes that have been occupied. Remove the old nests, clean them and make any repairs. Cleaning the boxes with a bleach-water solution (1:2 ratios) will help reduce parasites and diseases in the nests. The following spring, add fresh nesting material to all the boxes.
The package bumble bee industry, which provides farmers with live bumble bee colonies for crop pollination, currently only produces a single eastern bumble bee species, Bombs impatiens. This species is then shipped nationwide, in a situation similar to the blue orchard bee, often far beyond its native range. Many bumble bee scientists now believe that these commercially produced bumble bees are responsible for the introduction of one or more diseases which have decimated several bumble bee species, even causing the potential extinction of one species, Bombus franklini (Franklin's bumble bee).
There is an enormous need for managed agricultural pollinators in this country, but it critical not to import non-local bees, especially near wild areas, even if the bees are represented as being the same species as local bees. The alternatives are to either develop local commercial sources of bees that are native to your region or to rear already widely established non-native species, such as honey bees or the alfalfa leafcutter bee, as managed pollinators.
Cuckoo bumblebees are a few species of bees which live parasitically in the colonies of other bumblebees and have lost the ability to collect pollen (Figure 45).. Before finding and invading a host colony, a Psithyrus female (there is no caste system in these species) will feed directly from flowers. Once she has infiltrated a host colony, the Psithyrus female will kill or subdue the queen of that colony and forcibly (using pheromones and/or physical attacks) "enslave" the workers of that colony to feed her and her young. This female also has a number of adaptations, such as larger mandibles and a larger venom sac that increase her chances of taking over a nest.
Cuckoo Bumblebee. Image Courtesy of Alvesgaspar.
Queen and worker bumblebees can sting, but unlike a honey bees, a bumblebee's stinger lacks barbs, so they can sting more than once. Bumblebee species are normally non-aggressive, but will sting in defense of their nest, or if harmed. Female cuckoo bumblebees will aggressively attack host colony members, and sting the host queen, but will ignore other animals (including humans) unless disturbed. Based on my numerous encounters the sting of the bumble bees is considerably more painful than that of a honey bee.
Bumblebees are important pollinators of both crops and wildflowers. Bumblebees are increasingly cultured for agricultural use as pollinators because they can pollinate plant species that other pollinators cannot by using a technique known as buzz pollination. For example, bumblebee colonies are often emplaced in greenhouse tomato production, because the frequency of buzzing that a bumblebee exhibits effectively releases tomato pollen which is normally wind pollinated and therefore difficult to release from the anther.
Bumblebees are in danger in many developed countries due to habitat destruction and collateral pesticide damage. In Britain, until relatively recently, 19 species of native true bumblebee were recognized along with six species of cuckoo bumblebees. Of these, three have become extinct, eight are in serious decline, and only six remain widespread. Similar declines in bumblebees have been reported in Ireland, with 4 species being designated Endangered, another two species considered Vulnerable to extinction. A decline in bumblebee numbers could cause large-scale sweeping changes to the countryside, leading to inadequate pollination of certain plants. The world's first bumblebee sanctuary was established at Vane Farm in the Loch Leven National Nature Reserve in Scotland in 2008.
One common, yet incorrect, assumption is that the buzzing sound of bees is caused by the beating of their wings. The sound is actually the result of the bee vibrating its flight muscles, and this can be achieved while the muscles are decoupled from the wings—a feature known in bees but not other insects. This is especially pronounced in bumblebees, as they must warm up their bodies considerably to get airborne at low ambient temperatures. Bumblebees have been known to reach an internal thoracic temperature of 30 °C (86 °F) using this method.
The orchestral interlude "Flight of the Bumblebee" was composed by Rimsky Korsakov to represent the turning of Prince Guidon to visit his father, Tsar Saltan, in the opera The Tale of Tsar Saltan, however the music is considered to more accurately reflect the flight of a bluebottle fly rather than a bumblebee.
The music went on to inspire Walt Disney to have a bumblebee featured in his musical Fantasia and also sound as if it was flying in all parts of the theatre - the unsuccessful experimentation led to the music being excluded from the film and the eventual invention of surround sound.
Salvador Dali was inspired by the sound of a bumblebee to create one of his paintings Dream Caused by the Flight of a Bumble bee around a Pomegranate a Second before Awakening.
Orchid Bees. Euglossine bees, also called orchid bees, are the only group of corbiculate bees whose non-parasitic members do not all possess eusocial behavior. Most of the species are solitary, though a few are communal, or exhibit simple forms of eusociality. There are about 200 described species, distributed in five genera: Euglossa, Eulaema, Eufriesea, Exaerete and the monotypic Aglae, all exclusively occurring in South or Central America (though one species, Euglossa viridissima, has become established in the United States). The latter two genera are cleptoparasites in the nests of other orchid bees. All except Eulaema are characterized by brilliant metallic coloration, primarily green, gold, and blue (Figure 46).
A Nest of Orchid Bees.
Females gather pollen and nectar as food from a variety of plants, and resins, mud and other materials for nest building. Some of the same food plants are also used by the males, which however leave the nest upon hatching and do not return.
Male orchid bees have uniquely modified legs which are used to collect and store different volatile compounds (often esters) throughout their lives, primarily from orchids in the subtribes Stanhopeinae and Catasetinae, where all species are exclusively pollinated by euglossine males. These orchids do not produce nectar, and hide the pollen on a single anther under an anther cap; they are not visited by females. The whole pollinarium becomes attached to the male as it leaves the flower (Figure 47). Several flowers from other plant families are also visited by the bees: Spathiphyllum and Anthurium (Araceae), Drymonia and Gloxinia (Gesneriaceae),Cyphomandra (Solanaceae), and Dalechampia (Euphorbiaceae) contain one or more species that attract male euglossines.
A Male Orchid Bee with Highly Modified Legs. Image Courtesy Green Fly.
The chemicals are picked up using special brushes on the forelegs, transferred from there by rubbing the brushes against combs on the middle legs, and finally these combs are pressed into grooves on the dorsal edge of the hind legs, squeezing the chemicals past the waxy hairs which block the opening of the groove, and into a sponge-like cavity inside the hind tibia.
The accumulated "fragrances" are evidently released by the males at their display sites in the forest understory, where matings are known to take place. Although the accumulated volatiles have long been believed to serve as a signal to females, female attraction to male odors has never been demonstrated in behavioral experiments. The behavior of volatile collection is essentially unique in the animal kingdom. Single synthetic compounds are commonly used as bait to attract and collect males for study, and include many familiar flavorings and odors considered appealing to humans (e.g., methyl salicylate, eugenol, cineole, benzyl acetate, methyl benzoate, methyl cinnamate), and others which are not (e.g., skatole).
Neotropical orchids themselves often exhibit elaborate adaptations involving highly specific placement of pollen packets (pollinia) on the bodies of the male orchid bees; the specificity of their placement ensures that cross-pollination only occurs between orchids of the same species. Different orchid bee males are attracted to different chemicals, so there is also some specificity regarding which orchid bees visit which types of orchid. The early description of this pollination system was by Charles Darwin, though at the time, he believed the bees were females. Not all orchids utilize euglossines as pollen vectors, of course; among the other types of insects exploited are other types of bees, wasps, flies, ants, and moths.
Digger Bees. The Anthophorini is a large tribe in the family Apidae, with over 750 species worldwide that were previously classified in the family Anthophoridae; the vast majority of species are in the genera Amegilla and Anthophora. All species are solitary, though many nest in large aggregations. Nearly all species make nests in the soil, either in banks or in flat ground; the larvae develop in cells with waterproof linings and do not spin cocoons. Species in this tribe are often referred to as "digger bees", though this common name is sometimes applied to members of the tribe Centridini, as well (Figure 48).
Digger Bee, Image Courtesy of entomart.
The characters used to define this group are subtle, but they are nonetheless fairly recognizable; they are generally large (up to 3 cm), very robust, hairy bees, with visibly protruding faces, and the apical portion of the wings are studded with microscopic papillae. The abdomen is often banded, and in many Old World species of Amegilla these bands are metallic blue. The wings often appear disproportionately short compared to other bees, and their "buzz" is often a high-pitched whine, as they hover and feed on flowers. Males commonly have pale white or yellow facial markings, and/or peculiarly modified leg armature and hairs.
Attracting Digger Bees. Some digger bees nest in cracks or cavities in soft sandstone and dry exposed soil embankments. Some of these species will excavate tunnels in cliff sides by wetting the hard soil surface with water or nectar to soften it.
To attract these species, adobe bricks can serve as the equivalent of a wooden nest block. Such bricks can sometimes be purchased, in which case you can increase their attractiveness to bees by drilling nesting holes following the size recommendations listed above for wood blocks.
Adobe blocks can also be easily made where clay soils are common. To create one, half-fill a large bucket with clay soil, and then fill the bucket with water. Stir the mixture together to create muddy slurry and allow it to settle. Remove any sticks or debris floating on the surface and slowly pour off most of the water. Finally, pour the remaining sediment into a mold (such as a wooden box or small Styrofoam cooler), and allow it to dry for several days or weeks. Before it completely dries, you can make several 1-inch indentations, using the diameter guidelines above, to make it more attractive to bees.
Mount the brick, either singularly or in a stack. Adobe will not hold up well in wet climates and many need sheltering from rain. You might want to supply a shallow water source near your bricks to help bees excavate their nests.
Halictidae-Halictid Bees. This is a cosmopolitan family of the order Hymenoptera consisting of small (> 4 mm) to midsize (> 8 mm) bees which are usually dark-colored and often metallic in appearance. Several species are all or partly green and a few are red (Figure 49); a number of them have yellow markings, especially the males, which commonly possess yellow faces, a pattern widespread among the various families of bees. They are commonly referred to as sweat bees (especially the smaller species), as they are often attracted to perspiration; when pinched, females can give a minor sting.
Common Sweat Bee. Image Courtesy of Jon Sullivan
Most halictids nest in the ground, though a few nest in wood. They mass-provision their young by providing a mass of pollen and nectar formed inside a waterproof cell. Once an egg is deposited on this mass the cell is sealed off. Thus the larva is with all the food at one time that it needs for full development, as opposed to "progressive provisioning", where a larva is fed repeatedly as it grows, as in honey bees. All adult species are pollen feeders and may be important pollinators. Several genera and species of halictids are cleptoparasites of other bees (mostly other halictids). The most well-known and common are species in the genus Sphecodes, where the female enters the cell with the provision mass, eats the host egg, and lays an egg of her own in its place.
Halictidae are one of the four bee families that contain some species that are crepuscular. These bees are active only at dusk or in the early evening or sometimes truly nocturnal. In these cases they have greatly enlarged ocelli or simple eyes to enhance their night vision.
Megachilidae-Leaf Cutting Bees and Mason Bees. The Megachilidae are a cosmopolitan family of solitary bees (Figure 50) whose pollen-carrying structure (called a scopa) is restricted to the ventral surface of the abdomen (rather than mostly or exclusively on the hind legs as in other bee families).
Leaf Cutting Bee with Pollen Trapped on Underside of Abdomen.
Megachilid genera are most commonly known as mason bees and leafcutter bees, reflecting the materials they build their nest cells from (soil or leaves, respectively); a few collect plant or animal hairs and fibers, and are called carder bees. All species feed on nectar and pollen, but a few are cleptoparasites (informally called "cuckoo bees"), feeding on pollen collected by other megachilid bees. These parasitic species do not possess scopa and are incapable of collecting their own pollen. The brightly colored scopa leads to a colloquial name used occasionally in North America - "Jelly-belly bees." Megachilid bees are among the world's most efficient pollinators because of their energetic swimming-like motion in the reproductive structures of flowers, which moves pollen, as needed for pollination. One of the reasons they are efficient pollinators is their frequency of visiting to plants. In actuality they are extremely inefficient at gathering pollen when compared to all other bee families. However, megachilids require on average nearly ten times as many trips to flowers to gather sufficient resources to provision a single brood cell. Of course with more, more pollination is accomplished.
North America has many native megachilid species, but Alfalfa leafcutter bees (Megachile rotundata) are an imported species used for pollination. The most significant native species is Osmia lignaria (the "Orchard Mason Bee" or "Blue Orchard Bee"), which is sold commercially for use in orchard crop pollination, and which can be attracted to nest in wooden blocks with holes drilled in them (which are also sold commercially for this purpose).
Leafcutter bees nest in soft, rotted wood; thick-stemmed, pithy plants (e.g., rose); and in similar materials that the bees can easily cut through and excavate. Nest tunnels may extend several inches deep and coarse sawdust may be deposited at the entrance. This sometimes causes confusion with other wood nesting insects such as carpenter ants. However, leafcutter bees restrict their tunneling to soft, rotted wood and do not cause damage to homes or other wooden structures.
There also are concerns about leafcutter bee nesting in rose canes, excavating the pith of pruned canes. Leafcutter bees sometimes nest in the largest diameter rose canes but cause little damage because they restrict tunneling to the pith and rarely girdle cambium. Furthermore, other insects, including various hunting wasps (Pemphredon species) and small carpenter bees more commonly tunnel and nest in rose canes.
After the nest is made, the bees collect fragments of leaves to construct individual nest cells. The bees cut leaves in a distinctive manner, making a smooth semicircular cut about 3/4 inch in diameter from the edge of leaves. Although they cut many types of leaves, leafcutter bees prefer certain types, notably rose, green ash, lilac and Virginia creeper. This injury often is only a minor curiosity. However, where leafcutter bees are abundant and concentrate on cultivated plantings, the removal of leaf tissues can be damaging. Serious damage most often occurs in isolated rural plantings.
Rose Leaf with Discs Cut from Edge by Leaf Cutting Bee.
Leafcutter bees do not eat the cut pieces of leaves that they remove. Instead, they carry them back to the nest and use them to fashion nest cells within the previously constructed tunnels. Then they provision each leaf-lined cell with a mixture of nectar and pollen. The female lays an egg and seals the cell, producing a finished nest cell that somewhat resembles a cigar butt. A series of closely packed cells are produced in sequence. A finished nest tunnel may contain a dozen or more cells forming a tube 4 to 8 inches long. The young bees develop and remain within the cells, emerging the next season.
There are a great many parasites that act as important natural enemies of leafcutter bees. As a result, leaf cutting activity may vary widely from year to year. Parasitic bees and wasps, velvet ants and certain blister beetles are among the most important enemies of leafcutter bees and other solitary bees.
Alfalfa Leafcutter Bee-Megachile rotundata. This is a European bee that has been introduced to other regions . As a solitary bee species, it does not build colonies or store honey, but is a very efficient pollinator of alfalfa, carrots and some other vegetables.
The importation of the species to North America was to assist in the pollination of food crops, and it has now widespread. The species is also found in Queensland, Australia, but not recorded in other states. The vernacular in Australia is Lucerne leafcutter bee.
Female alfalfa leafcutter bees have stingers, but both sexes will use their mandibles as a defensive mechanism, usually only defending themselves when squeezed or antagonized. Therefore bee suits, such as those required with honey bees, are not really necessary when dealing with these bees. The ratio of males to females is generally one to one.
Alfalfa Leaf Cutting Bee. Image Courtesy of USDA.
This species of leafcutter bee is cultivated to pollinate alfalfa grown for seed, a function that it does far more efficiently than honeybees. These leafcutter bees are provided with predrilled "bee boards" that they use for nest construction. At the end of the season, the nest cells with developing bees are collected and carefully stored, to be released the subsequent season when alfalfa blooms.
Figure 53. Alfalfa Leaf Cutting Bee Pollinating Alfalfa.
Commercially produced bee blocks, consisting of a wood block drilled with a series of dead-end holes, are now widely available. These types of bee nests were initially developed in the 1960s by alfalfa seed producers in the western United States to attract and manage large numbers of the non-native alfalfa leafcutter bee (Megachile rotundata). Their sole purpose is to attract wild populations of these bees.
Bee Block for Attracting Large Population of Alfalfa Leaf Cutting Bees.
More recently they have been modified to manage the blue orchard bee (Osmia lignaria), a bee that is active only in the spring and will not pollinate later-flowering fruits and vegetables. Consequently, all of the nest tunnels are a uniform size and depth, which may be either too large or too small for many other species. Nest blocks with a greater diversity of hole sizes and depths are necessary to attract a variety of bees that are active throughout the year.
Under the best circumstances these nests can attract large numbers of cavity-nesting bees and boost their local populations. However, because these nests concentrate bee populations in unnaturally large numbers in a small space, they can become infested with parasites and disease spores after several seasons.
Without regular sanitation or the phasing out of nest materials, these parasites and diseases threaten long-term pollinator health wherever they are used. Because contaminated nest blocks left unattended in the landscape continue to attract wild bees from the surrounding area, they have the potential to do harm. Only with proper management can these nests maintain healthy bee populations indefinitely.
Alfalfa flowers provide an example of native bee efficiency. The stamen (the structure holding the anthers) of alfalfa flowers is held under tension by two flower petals, and springs forward with force when released by a visiting bee. This triggering discourages many bees, including honey bees, which learn to avoid being hit by the stamen by approaching the flower from behind, where they can gather nectar but not pollen. The alkali bee (Nomia melanderi), a native ground-nesting megachilid bee, is not discouraged by this unusual flower structure and is a major pollinator of alfalfa seed in some western states. It has been used as an effective pollinator of alfalfa when grown for seed in the western United States. In this case large areas of barren soil are provided for the nesting of this bee,
Mason Bees. These are a gentle beneficial insects that has potential as a pollinator of apples, cherries, and other tree fruits. It is found throughout most of North America, particularly in wooded areas but often around homes in towns and cities.
Mason Bees. Image Courtesy of Exzellente Bilder.
Homeowners sometimes become concerned when they see the bee entering cavities under shake siding or investigating nail holes or other cavities in wood during March through early June. These are not destructive insects, since they do not excavate holes in the wood, though they will clean out loose debris. No controls are recommended, since no damage is done. To prevent the bee from nesting, holes may be filled with caulking.
The females use existing holes in wood for a nest. They choose holes slightly larger than their body, usually 1/4 to 3/8 inches in diameter. The bees first place a mud plug at the bottom of the hole, then brings in 15 to 20 loads of nectar and pollen which they collects from spring flowers, including apples and other fruits. If you watch the bees closely as they enter the nest, you can see the pollen on the underside of the abdomen.
When the female has provided a sufficient supply of food for the larva, she lays an egg and then seals the cell with a thin mud plug. She then provisions another cell, and continues in this fashion until the hole is nearly full. Finally the bee plasters a thick mud plug at the entrance. Some wasps and leaf-cutter bees also build nests in such holes but their nests can be distinguished from the orchard mason bee nests by characteristics of the plug. The plug of the mason bee is always rough while the wasp prepares a smooth plug. Leaf-cutters seal the holes with chewed-up leaves.
Mason Bee Egg in Pollen Mass. Image Courtesy of Red58bill
The female mason bee lives for about a month and can produce one or two eggs each day. The larva hatches from the egg after a few days and begins to eat its provisions. When the pollen-nectar mass is completely eaten in about 10 days, the larva spins a cocoon and pupates within the cell.
Near the end of the summer the bee transforms to the adult stage but remains in the cocoon throughout the winter. In the spring, when the weather has warmed up sufficiently, the males begin to emerge by chewing their way out of the cocoons and through the mud plugs. The females, which are almost always in the inner cells of the tunnel, emerge several days later. One or two weeks may be required for all the bees to emerge during cool weather.
Females mate soon after emerging and begin nesting in 3 to 4 days. The bees forage on a number of different flowers. In wooded areas, they seem to prefer ballhead waterleaf. In urban areas, dandelion and Oregon grape are commonly visited, in addition to cherries and apples.
The mason bee is non-aggressive and will sting only if handled roughly or if it should get trapped under clothing. It is less objectionable than the honey bee as a pollinator in urban areas and should be encouraged. Efforts are being made experimentally to develop large populations of these bees to use as a supplement to honey bees for fruit pollination, much as the alfalfa leaf cutting bee was developed for alfalfa seed pollination.
Populations for pollinating around a home or commercial orchard can be developed by establishing trap nests to collect the bees. Trap nests can be made by drilling holes 1/4 to 3/8 inches in diameter and 3 to 6 inches deep in pine or fir 4x4's. A "brad-point bit" leaves a nice, smooth hole. (Figure 57) Alfalfa leaf cutting bee boards with hole diameters of at least 1/4 inch can also be used. These boards are then attached to a house or other structure where bees have been seen. Some protection from rain is desirable. Boards can also be placed on dead trees or posts in wooded areas near streams where there is a good supply of mud for nest construction and wild flowers on which to forage.
Predrilled Drilled Block Infested with Mason Bees. Image Courtesy of Red 58bill.
Boards should be positioned where they will receive morning sunlight and started in March before the bees begin nesting and remove them in early to mid-summer when nesting is completed. If the boards are stored outdoors over winter (under cover to protect them from rain and snow) the bees will usually emerge in March and April. They should forage for pollen during the period of cherry and apple bloom and afterwards, if sufficient other flowers are available to them.
For large populations for orchard pollination, the nests should be under humid refrigeration at 35 to 40° F. This will permit control of emergence time and reduce predation and parasitism by the insect enemies of the bees. Do not place the nests in storage until September or October to assure complete development of the adults. The following spring, place the boards in the orchards in plywood shelters facing east to catch the morning sun. To hasten emergence, incubate the boards at room temperature for 24 hours before placing the bees in the orchard. The boards and some new nesting material should be in place a few days before apples begin to bloom, or earlier if other fruit bloom such as cherries, is available. Provide 500-1000 filled holes per acre. These should contain 750-1000 females, assuming an average of 1 1/2 females per hole. Males also visit flowers, but they do not live long and are not as effective as pollinators. Competing flowers such as dandelions should be mowed as soon as the fruit begins to bloom.
Developing large populations of the bees may be a slow process under orchard conditions; the short duration of bloom does not allow the bees to accomplish maximum reproduction. The orchard mason bee also has a tendency to fly away rather than using or reusing nests in the near vicinity. However, relatively large populations have been developed in 2 or 3 years in urban situations. Once established, orchard bees will nest in containers filled with large-diameter drinking straws or paper tubes folded in half.
Orchard Mason Bee, Osmia lignaria. This is a megachilid bee that as do other mason bee makes nests in reeds and natural holes, creating individual cells for their brood that are separated by mud dividers. They are unlike carpenter bees in that they cannot drill holes in wood. O. lignaria is a common species used for early spring fruit bloom in Japan, Canada, and the United States, though a number of species of other Osmia are also cultured for use in pollination.
Orchard Mason Bee. Image Courtesy Red58bill.
The bees begin to emerge from their cocoons in the spring when the daytime temperature reaches 14°C (57°F). The males emerge first. They remain near the nesting site and wait for the females to begin their emergence, which can be several days to weeks depending on the number of days of warm weather. The first thing the females do is mate. A female will typically mate once, maybe twice. She will be absent from the nesting site for several days while she feeds and waits for her ovaries to fully mature.
When a female is ready, she seeks out a suitable nest. O. lignaria females like to nest in narrow holes or tubes, though they have been found to nest inside cedar shakes and even keyholes. Beekeepers put out pre-made nesting materials to entice the females to stay close to the orchard. Rain, wind, and free-release (the practice of putting loose cocoons out rather than letting them emerge in their natal nests) discourage females from selecting a nesting site near their natal nest. A female might inspect several potential nests before settling in. Once she has found the right nest, she flies outside of the hole and does an in-flight dance. She is orienting on major visual features in order to find her nest when she returns from foraging.
O. lignaria arrange their nest as a series of partitions, with one egg per partition. She begins the process by collecting mud and building the back wall of the first partition. Then she makes trips to nearby flowers. Unlike honey bees which visit flowers that are miles away, she prefers flowers that are nearest the nest. She can visit 75 flowers per trip, and it takes 25 trips to create a complete pollen/nectar provision. She works tirelessly during the day, only stopping once the sun has gone down. When the sun rises the next morning, she will bask in its rays until she is warm enough to fly. Then she continues where ever she left off the day before.
Once the provision is complete, she backs into the hole and lays an egg on top of it. She collects more mud to seal off the partition. The new wall also doubles as the back wall of the next cell. She continues until she has filled the nest hole. O. lignara, like many insects, can select the gender of the egg they lay by fertilizing the egg, or not. Unfertilized eggs are males, while fertilized eggs are females. The adult bee lays female eggs in the back of the burrow, and the male eggs towards the front. She lays about three males to every nest hole depending on depth.
When the egg hatches, the larva consumes the food provision as it goes through many changes on its way to becoming an adult. It will spend most of its life alone in this dark cell made by its mother.
Once the female has finished the nest, she plugs the entrance with one thick mud wall. Then she seeks out another location for a new nest. She works tirelessly until she dies. An O. lignaria female lives for about four to eight weeks and she can complete an average of four 6-inch tubes in her lifetime, with about eight eggs per tube. That's nearly 60,000 blossom visits per female. Because of this farmers have cultivated the insect for pollination purposes in fruit orchards.
By the early summer, a larva has consumed all of its provisions and begins spinning a cocoon around itself and enters the pupal stage; the adult females die off as the season progresses.
The young bee is now a fully developed insect and diapauses inside its cocoon for the duration of the winter. They burn through their fat reserves to stay warm. If it stays cold for too long, the bees can die of starvation. Alternatively, if the temperature rises too fast, they may emerge before the blossom. Farmers are known to exploit their emergence cycle and time their release to coincide with the first orchard blossoms.
Commercial Availability. Recently, many people have become interested in the blue orchard bee (Osmia lignaria), also called the orchard mason bee, as a garden and orchard pollinator. Many thousands of mason bee nesting blocks are sold each year in the United States, along with hundreds of thousands of blue orchard bees. This interest has greatly raised public awareness about the importance of pollinators; however, it is important to remember that raising large numbers of a single species (bee-ranching) is a different objective than the conservation of diverse species of wild pollinators.
As mason beekeeping has increased in popularity, important questions are being asked about the risks associated with the nationwide shipment of blue orchard bees by commercial producers. In fact, there are two distinct subspecies of the blue orchard bee: Osmia lignaria propinqua in western North America and Osmia lignaria lignaria in the east. The species is rare in the Great Plains region, although some intermediate specimens have been collected.
Most commercial producers of the blue orchard bee are located in the Pacific Northwest, where they rear the locally native western subspecies . Unfortunately, the bees these producers raise are then marketed nationwide, resulting in the frequent shipment of locally non-native bees to the eastern United States. The potential ecological consequences of the western blue orchard bee hybridizing with its eastern subspecies are unknown. Similarly, these shipments have the potential to introduce locally non-native parasites and diseases. For the consumer, there is another significant drawback. The western bees may not develop in sync with local conditions, resulting in poor establishment and poor performance as pollinators. The net result is that people purchasing blue orchard bees over the Internet or through garden catalogs may be doing more to harm their local pollinator populations than to help them – and not be getting the pollination they paid for.
This is a family of bees that are often referred to collectively as plasterer bees, due to the method of smoothing the walls of their nest cells with secretions applied with their mouthparts; these secretions dry into a cellophane-like lining. This allows the bees to nest in periodically flooded areas such as stream banks. There are over 2000species, all of them evidently solitary, though many nest in aggregations. Bees in this are highly varied in appearance and have few common features. One feature consistent to all colletid bees is that their tongue has a branched tip (Figure 59) . The two genera most frequently seen are Colletes and Hylaeus.
Two of the subfamilies, Euryglossinae and Hylaeinae, lack the external pollen-carrying apparatus (the scopa) that otherwise characterizes most bees, and instead carry the pollen in their crop (enlarged portion of the foregut). These groups, and in fact most genera in this family have liquid or semi-liquid pollen masses on which the larvae develop.
Colletid Bee. Image Courtesy of Michael Becker.
They can be found all over the world, but the most species live in South America and Australia. Over 50% of all bee species living in Australia belong to this family. Only the genera Colletes and Hylaeuscan be found in Europe, while in North America there are, in addition to these two, the genera Caupolicana, Eulonchopria, and Ptiloglossa.
Ants are among the most highly evolved of insects. The variety of lifestyles displayed by ants is amazing--perhaps because so many of their social behaviors seemingly parallel our own.
All living ant species have a caste system. The main castes consist of kings, queens and workers. The kings are winged reproductive males that contribute absolutely nothing to the labor of the colony. The winged females swarm with the males, similarly to the behavior previously discussed with termites. Eventually they will become the queens of new colonies. During the establishment of a new colony, the new queen initially performs all the work tasks; but once her first brood of worker larvae is reared to adulthood, her sole duty is to lay eggs. Unlike termites, ant colonies may have many queens, in some cases, hundreds.
Workers are sterile females and can be both the laborers and defenders of the colony. In most ant species there can be sub-castes of the workers, namely majors, media and minors. Relative head and overall body size distinguish subcastes. The majors are the largest of the three and possess a disproportionately large head and mandibles. The function of the soldiers is to protect the ant colonies. The media and minor workers are the most common individuals in an ant colony and perform the majority of the work duties. Minor worker ants also perform a variety of functions depending on the species of ant.
Ant Wars, Competition and Survival. Ants are amongst the most aggressive and war-like of all animals. If ants had a policy of life it could be summarized as restless aggression, territorial conquest, and total annihilation of neighboring colonies. These insects use any of a number of strategies and weapons to reach these ultimate goals. Chemical warfare is prevalent amongst many species including spraying a variety of toxic chemicals in order to repel, confuse, immobilize or even kill their rivals. The soldiers of many species readily assume a kamikaze role in order to “win skirmishes” between rival colonies. One of the most dramatic of these sacrifices is exhibited by a carpenter ant from SE Asia. These ants act as walking bombs. There is a huge internal gland that occupies much of their body that is filled with toxic chemicals. If one of these ants is hard pressed by a rival ant or predator it contract some large abdominal muscles that bursts open the abdomen violently (like a bomb) releasing the chemicals.
The availability or more significantly the limited availability of food frequently is important in colony survival. As a consequence rival colonies frequently develop strategies to maximize their collection of available food. There is a tiny fast moving ant in the deserts of Arizona that utilizes toxic secretions to intimidate and confuse much large honey ants (10 time their size) as they steal food from the larger ant colonies. In addition these tiny ants will frequently prevent honey ants from leaving their nests by releasing toxic chemical down the hole or nest entrance thus driving the former below ground. This of course allows the smaller species to forage without competition from the honey ants. Another form of nest entrance blocking is exhibited by a small ant species in the southwestern deserts. In this case they gather in mass around the nest entrance of their rivals and similarly release toxic chemicals down the entrance. However in addition they pick up pebbles, twigs and other small objects and drop them down the vertical shaft entrance.
Possibly the most elaborate of all documented aggressive strategies in social insects occurs in battles between the tiny woodland ant and the imported fire ant. The fire ants are deadly enemies of the woodland ants with colonies 100 times larger than their tiny rivals. Even though fire ants are much more powerful than the woodland ants both successfully survive in the same area. The secret of woodland ant survival evolves around a specialized soldier (major) and a three-stage strategy to defend against fire ant attack. These soldiers are equipped with huge heads that are equipped with large sharp jaws provided with massive muscles. These do not attempt to sting or spray their enemy with poisons (common in many ants) but quite precisely use their mandible to snip off legs, heads and other body parts. Unless attacked the majors remain in the colony. However, the minors regularly forage for food but are always on the alert for scout fire ants that are looking for colonies to raid. If a woodland ant minor encounters a fire ant soldier close to its colony a violent response is triggered. Once detected the minor rushes to the fire ant in a mock attack but merely touches the potential invader in order to acquire some of its odor. She then quickly retreats toward her nest. As she retreats she lays a pheromone trail by periodically touching her abdomen to the ground. On her way back she briefly rushes up to any other minor alerting them to the presence of the fire ant scout. Once in the nest soldiers plus many of the minors are alerted to the presence of the invader scout (by its smell on the minor worker) they subsequently rush in mass along the already establish pheromone trail leading to the enemy. Once found the soldier surrounds the fire ant and attack relentlessly and are fully capable of destroying it due to their great superiority in numbers. Of course the whole purpose is to kill the fire ant scout before it can alert other fire ants in the area as to the presence of a woodland ant colony. Once accomplished the soldiers search the general area for any other fire ant scouts.
If fire ants mount a full scale attack of a woodland ant colony, the defenders have an alternate strategy. As fire ants arrive in full force the entire force of woodland soldier ants are sent into the battle. Soon the battle ground is littered with the bodies of the smaller species plus a multitude of legs and other body parts of the fire ants. As the battle continues any woodland ant minors still present retreat to the nest. As more and more fire ants arrive and the woodland ant soldiers are greatly out-numbered they retreat, close ranks to form a dense protective perimeter around their colony entrance. With the impending doom that the fire ants will soon break through the protective barrier and ravage, steal and consume the woodland ant’s eggs, larvae and pupae the activity of the minors in the colonies is frantic but well programs. They gather the young in their mandibles and sprint out though the colony entrance, through the battle field and beyond to safety. The woodland ant soldiers remain true to their programmed behavior and fight to the death. Once the fire ants leave the now ravaged colony the minors return with their cargo of eggs, larvae and pupae and reestablish colony life. Over time new soldiers develop in the colony preparing for the possibility of another raid. Such is the life of ants!
Some ants survive by controlling the environment in which they live. In the Amazon rain forests there is a tremendous diversity of vegetation. If you walk through the forest no plant typically dominates and you may not see any two plants of the same species within hundreds of yards. One notable exception is the Cordia tree. On occasion you will find a large stands of these trees with no other plants in the vicinity. In addition these stands are typically encircled by large barren strips of land. The reason for this phenomenon is the presence of a small ant species that lives within the stems of these trees. They are very protective killing any plant feeding insects. They will also swarm on and attack any larger animal venturing into the stand. In addition any other species of plants that germinates with in the stand quickly shrivels and dies due to the ants stinging and injecting venom into the terminal buds. As might be expected the barren areas surrounding the stand of trees is similarly cleared by the stinging of these ants. Of course the ants benefit from this symbiotic relationship since they are provided by a safe bountiful location for their nests. And of course the trees benefit as they are provided with an endless competitively free environment in which to expand their growth. People living in the rain forest refer to the barren areas as the “devil’s garden” and refrain from planting crops there.
Honey Ants. Ants vary tremendously as to their food preferences, size and colony locations. The honey ants are among some of the more interesting species. Normally they live in arid desert regions of the world; their primary diet is honeydew, which they collect from aphids and other homopterans. In such dry areas, honeydew-producing insects are common during the rainy season only when host plants prevail. Because in most areas this season only lasts a few months, honey ants have developed a means of ‘storing’ honeydew from season to season. A special form of worker called the replete, or reservoir ant, accomplishes this. These repletes are fed huge amounts of honeydew; consequently, their abdomens stretch to many times the normal size. Once fed, reservoir ants remain inactive and store honeydew for many months. In many areas of the world, reservoir honey ants are human’s food—they are collected and their abdomens are bitten off. The stored honeydew gives them a candy-like taste.
Honey Ants-Myrmecocystus Spp..
Worker media and replete castes of honey ants. Image courtesy Greg Hume at Wikepedia.
Colonies of these amazing insects develop specialized workers, called repletes or honeypots, with tremendously swollen abdomens for nectar storage. Some repletes also hoard water, fats and body fluid from insect prey. The repletes ingorge on food that is collected outside the nest and brought to them by normally-proportioned worker ants. Deep in underground chambers, the repletes hang quietly in clusters, literally imprisoned by their abdomens ballooned to the size of small grapes (Figure )!
Worldwide there are several very different kinds of ants that exhibit extreme repletism; all are properly called honey ants. One outstanding group; the genus Myrmecocystus, occurs exclusively in western North America. Myrmecocystus contains a diverse ensemblage of at least 28 closely related species, many of which are broadly distributed. It follows that these honey ants are very common insects. Most human residents or visitors to the American Southwest have probably strolled atop a honey ant nest completely unaware of the treasure trove hidden below. But those lucky enough to view repletes first hand can't help but want to find out more about these astonishing creatures.
Honey ants are highly social insects. They live in efficiently organized colonies or groups of cooperating individuals. Their societies are matriarchal or female-dominated families. A typical honey ant colony contains a single fertile queen and thousands of sterile female workers. The queen is the mother of the colony and is specialized for egg production, while the workers, the queen's daughters and hence all sisters, are responsible for colony labor.
Worker honey ants are polymorphic, meaning that they come in different sizes, ranging ten-fold or more in body weight. This variation, in turn, permits more effective task specialization. For example, the smallest workers, called minims, tend to remain in the nest as nursemaids caring for the queen, the developing brood (eggs, larvae and pupae) and the repletes. Medium and larger size workers are more apt to be involved with nest excavation, food acquisition and colony defense. The largest workers, called majors, are the individuals most likely to develop into repletes. Honey ant colonies are coordinated largely by pheromones, glandular secretions produced by the ants that function as chemical signals. Pheromones regulate complex social behavior and broadly serve to identify colony members, recruit nestmates to food sources, and elicit alarm and defensive behaviors. For example, honey ant workers instantly distinguish nestmates from intruders based on their smell (colony odor); the former might be groomed and offered food while the latter would be attacked and killed or driven from the nest.
Honey ant societies may also contain numerous non-working reproductive forms, or winged males and virgin queens. Winged forms, called alates, are produced when colony populations reach an optimal size and become reproductively mature. Then, a portion of the brood raised each year is converted into individuals designed to mate, disperse and start new colonies. Mating flights typically are nocturnal or crepuscular, and generally occur only once a year following the first heavy precipitation of the summer rainy season.
The reproductive forms pour out of the nest and swarm into the air, mating on the fly. Young queens take only one mating flight; they store viable sperm long-term in a special organ, called a spermatheca, which is then used for fertilizing eggs throughout the remainder of their lives.
The males, their primary function completed, die shortly after mating. The inseminated queens drop to the ground, twist off their now useless wings, and scamper across the surface of the warm wet ground, looking for a place to burrow. The vast majority of the queens fall victim to a barrage of predators including birds, lizards, spiders and especially, other ants. Surviving queens must be well below ground before the rising sun relentlessly dries and bakes the surface. The queens seal themselves inside humid, subterranean cavities and do not forage; rather, they rear their first brood of tiny workers, called nanitics, relying solely on their stored fat reserves and metabolized flight muscles. Colony growth is slow at first, but soon rapidly accelerates as additional ants are added to the worker force.
Honey ant nests almost always have only a single surface opening surrounded by a small accumulation of excavated substrate. Each species has a characteristic nest entrance. For example, M. mimicus builds a low sandy mound while M. mexicanus constructs a turret of coarse gravel. Nest openings of the latter species are very distinctive and not easily confused with those built by other kinds of ants in the area. The amount of soil surrounding a honey ant nest entrance is deceptively small, for the nest tunnels and chambers frequently extend deep into the ground, often reaching several yards or more below the surface. Nests of M. mexicanus have been studied in detail and have a surprisingly distinct and seemingly adaptive architecture. The nests typically are built in hard rocky soil, and consist of a subsurface labyrinth of tunnels and a vertical array of small domed chambers interconnected by one narrow vertical passageway. The maze of tunnels just below the surface probably serves as a staging area for foraging parties and mating flights and as a site for brood incubation. The lower chambers, deep enough to be within the level of permanent soil moisture, house the queen, much of the worker population and the majority of repletes. The lone interconnecting passage probably makes individual nest chambers easier to defend or seal off from enemy invaders.
Honey ants are generalized scavengers and predators. Sugary carbohydrates are needed for energy. The ants visit flowers and extrafloral nectaries for the sweet rewards, and "milk" homopterans like aphids and scale insects for their sugary exudations called honeydew. Once engorged with liquid sugar, workers return to their nest to share with other colony members.
Protein sources also are necessary, particularly for the growing larvae. Foraging honey ants search for live or recently dead invertebrates, predominantly arthropods; small soft-bodied insects like termites and caterpillars are especially fair game. Individual workers head homeward with pieces of food clasped within their mandibles, while groups of workers may cooperate when retrieving large or struggling prey items.
Like all formicine ants, honey ants lack stingers: rather, they spray fine droplets of formic acid from their abdominal tip. The caustic acid is used, along with pinching mandibles, to help subdue uncooperative prey or to deter colony enemies. Grappling with prey or facing off against their foes, attacking honey ants spread and brace their legs, rapidly curl their abdomens underneath pointing forward, aim and fire. Their chemical weaponry is most effective against small targets; it is useful against mammals or other large animals only if sprayed into highly sensitive tissues like eyes or nostrils.
Given an abundance of sweet repletes, it is not surprising that badgers and other desert creatures sometimes burrow into and plunder honey ant nests. Even some honey ant colonies will raid one another, stealing not only repletes but also brood, that when mature, is "enslaved" as part of the pirating colony's worker force.
As recently as early this century, various Native American tribes and Mexicans regularly excavated honey ant colonies to obtain the savory morsels stockpiled therein. Sweet-toothed human predators typically hold a replete's head and thorax with the fingers, bite off or rupture the fragile abdomen, then suck its contents into the mouth. The so-called "honey" tastes somewhat like molasses, while the ants' bodies, being bitter, are discarded. Perhaps fortunately for honey ants, this practice seems to have fallen by the wayside due to the advent of commercially available candies. These not only taste better but are much less work to procure.
Many social insects, notably honey bees and some wasps, collect and store liquid sweets for later use. However, these insects stow their food within the confines of their nest combs. Honey ants are unique in using their own bodies as living storage vessels.
But why develop repletes? In arid regions, food and water usually are obtainable only for very limited periods. But when available, as during the brief summer rainy or growing season, these resources are present in overwhelming abundance. Under favorable conditions, surplus food gathered by the colony is fed to the repletes for long-term storage. Then, in times of need, the food is regurgitated back to colony members.
While the formation of food-storing repletes seems remarkable, it is merely an exaggerated form of typical ant behavior. Most ants possess expandable abdominal crops (stomachs) for temporarily carrying liquid food back to the nest. When solicited by a hungry nestmate, they regurgitate this liquid and offer a small droplet held between their mandibles. Close observation will reveal that the donor ant's abdomen shrinks as the recipient's abdomen expands. Thus, the crop serves as a "communal stomach" and repletism simply as extreme development of this expandable organ.
In the presence of excess food, repletes can develop from any newly emerged worker, apparently before its exoskeleton and intersegmental membranes harden and become less flexible. In young colonies, it is not uncommon to find small workers serving as somewhat ineffective repletes, with their tiny abdomens distended to the bursting point. However, on an individual basis, major workers make the most efficient honeypots. Hundreds to a thousand or more large repletes can be found in mature honey ant colonies, each patiently hanging and waiting to serve up dinner when called upon by its nestmates.
Argentine Ant. Linepithema humile.
Argentine Ant tending soft scale for honeydew. Image courtesy Penarc.
Identification. The Argentine ant is a one node, small, shiny, brown ant with only one size of worker. Workers are usually about 1/12 to 1/8 inch long. The queen ants are much larger, sometimes reaching 1/4 inch in length. They nest outdoors under logs, concrete slabs, debris and mulch. Argentine ants build very large colonies and can move rapidly. During winter months, this ant will move indoors.
Biology. This ant is successful and hard to control because:
· Different Argentine ant colonies in a same general locale are not enemies. Even the many queens in a single colony or separate colonies are friendly to each other.
· Argentine ants are not too "picky" when choosing a suitable site to infest or colonize. They readily (as you will read about in move their nests during the changing seasons and other conditions.
· These pests are omnivorous; they seem to never be in short supply of food.
· Each colony of Argentine ants contains a multitude of workers.
· Each worker is more courageous and harder worker than most ants. Creatures that attempt to prey on Argentine ants are confronted with an army of stubborn bugs that never runs from a fight!
· The queens of most ant species are usually egg-laying machines. The queen ant of Argentines actually helps in the care, grooming and feeding of her young.
· Most species of ants mate and reproduce by swarming; the Argentine mates in the colony, unexposed to the perils of birds, frogs, lizards, predator insects and extreme weather conditions. A swarmer reproductive (as seen with fireants and carpenter ants) has about 1 chance in 1,000 of surviving and successfully reproducing. The Argentine ant queen always succeeds!
Distribution. Originating from Northern Argentina near the Paraná River and surrounding regions, the Argentine ant now occurs in most regions with Mediterranean climates or with mild winters and moderate to high humidity. Argentine ants are established in at least 15 countries on six continents and many oceanic islands, including New Zealand, Japan, and Hawaii. The global distribution of Argentine ants continues to expand. Humans have been the primary factor in their spread, however, this ant can also disperse into new areas without human influence. The Argentine ant is widely distributed in California, with highest abundance in coastal areas, along rivers, and in urban settings.
It was discovered by scientists two years ago that native Argentine ant (in Argentina)colonies living in close proximity were territorial and aggressive toward one another, literally tearing one another apart whenever they came into contact. The puzzling question to the researchers was, Why weren’t the introduced ants in California the same way? Why would an Argentine ant from San Diego dropped into a colony in San Francisco be welcomed, while an Argentine ant dropped into a colony two hundred meters away in its native country be torn apart?
In search to the answer to that question the genetic differences among the ants in Argentina were compared with those in various parts of California, from San Diego to Ukiah. Using some of the same DNA fingerprinting techniques employed by criminologists, it was discovered that the native Argentine ants were twice as diverse as the native California ants, explaining why the California ants regard individuals up and down the coast as close kin, while those different nearby colonies in Argentina do not. They have an innate ability to recognize other members of their colony based on how genetically similar they are to themselves. Basically the genes are similar among California ants because they are descended from a relatively small founding population In essence, the super colony that we see in California is in fact one big colony.
Damage. Because it does not sting or bite the Argentine ant is not a direct threat to humans, unlike harvester ants or fire ants. However since there is little competition between opposing colonies of this species (one giant colony) this ant is the dominant species in areas where it becomes establish. It is very aggressive toward other species of ants and tends to out competes and replace other ants that are found in their same general area. As a result the Argentine ant is by a long way the major nuisance pest in urban areas, especially because of the availability of water. This ant exists in back yards at high densities associated with landscape features that provide favorable microclimates, such as potted plants and walkway bricks or stones. They enter homes through cracks and other spaces, in search of food or water.
Argentine ants are also an economic threat because of their potential to tend plant pest insects, such as mealybugs, scales, and aphids. In return for sweet honeydew secretions from these plant feeding insects, ants provide protection from natural enemies. Argentine ants may even move pests to better food sources or more favorable microclimates to maximize honeydew production. This mutualism can compromise management of pest insects by otherwise effective natural enemies, through removal or intimidation of predators and parasitoid wasps, leading to higher pest densities and greater plant damage than would occur in the absence of Argentine ants. For example, parasitism rates of an important citrus pest, the California red scale (Aonidiella auranti), were reduced two- to five-fold in the presence of Argentine ants.
Control. There are no known specific enemies of the Argentine ant. Therefore control is primarily via chemical and cultural means. Broadcast spraying of insecticides is of limited value because a substantial portion of Argentine ant colonies exist below ground where insecticides are unable to penetrate. Poison bait stations have proven effective at controlling Argentine ants in vineyards, though prolonged deployment may be required for natural enemy-mediated reductions on honeydew producing pests to become apparent. Control in homes and yards include sanitation (e.g. removal of food scraps), closing points of entry to homes, and removing landscaping features that promote favorable microclimates - especially excess water sources.
Leaf-cutting Ants. These are commonly found in many New World tropical areas. In such areas, columns of these ants frequently can be seen crawling up the trunks of trees and cutting small discs from the leaves. In some areas these insects are so common that they become major agricultural pests.
Leaf cutting ants carrying leaf discs.
Some of these ants exhibit polymorphism (different form within a caste –in this case the workers) to an extreme. There are 4 different forms within the worker caste, namely the minima, minors, media and maxima. The minima are the smallest form of the adults and function to care for the brood (larvae and pupae) and fungal gardens. Media workers forage for and carry the leaf discs deep into their nests, where they are licked, cut into smaller pieces, dampened with an anal secretion and finally formed into a bed of moist pulp. The newly formed beds are then planted with fungi from established beds. As the fungus grows, it is harvested and fed to the larvae. Most leaf cutting ants are quite particular and typically cultivate and harvest only one species of fungus. Media workers continuously ‘weed out’ any alien species of fungi that infest their gardens. It is believed that a few species actually produce fungicidal substances from their salivary glands, which chemically aid in the weeding process. In some species, when the swarming queens leave the colony, they carry the strands of fungi with them in pouches below their heads. Once new colonies are begun, the strands are ‘planted’ to assure a new garden of the correct species of fungi. The maxima are the largest of the forms with enlarged heads and protruding mandible. These of course are the soldiers of the colony and function to protect the colony against intruders.
In a few species of leaf-cutting ants, the minor caste performs a rather specialized function. These smaller workers frequently accompany the larger foraging leaf-gatherers; they do not assist in leaf cutting; but ride back to the nest either on the leaf portion or on the thorax of the media. Their sole function is to protect the media by snapping their mandibles at a species of parasitic fly that attempts to lay eggs on the media’s head.
Carpenter Ants. On occasion, carpenter ants are confused with termites by the homeowner. These two are easily distinguished by any of a number of characteristics. As in all ants, the abdomen is connected to the thorax by a narrow waist, or petiole, while the abdomen of a termite is broadly joined to the thorax. Also, in the winged forms, a termite’s wings extend far beyond the tip of the abdomen and their front and hind wings are of equal size and shape. In winged ants, the hind wings are much smaller than the front wings and both rarely extend beyond the tip of the abdomen. Many carpenter ants are large and typically black in color. Unlike termites, carpenter ants do not eat wood and rarely cause damage to structures. In California, their nests may occur inside the wooden parts of homes, but in such cases they usually have occupied abandoned drywood termite nests. Carpenter ants eat a variety of things, including other insects.
A common carpenter ant.
Army Ants. The most spectacular and well-known ants are the legionary, or army, ants of the humid tropical forests. These ants do not construct nests, but form temporary clusters called bivouacs in the shelter of fallen trees or in other partially exposed situations. The workers form a solid mass up to a yard wide, which consists of layer after layer of individuals hooked together by their tarsal claws. The queen, larvae, pupae, and eggs are located in the center of this mass.
An army ant, not considered as dangerous to humans as commonly believed.
The night is passed in a tight cluster, but at the first sign of light the cluster dissipates and hoards of workers fan out from the bivouac in all directions. Soon, one or more columns form and begin to search for food. The workers lay down a pheromone trail for others to follow while the soldiers guard the perimeter of the trail. Workers form numerous columns; changing positions behind the advancing hoards of ants—flushing out large numbers of prey (arthropods, small reptiles and rodents). The prey is stung, killed and transported to the rear as food for the larvae. At the end of the day the cluster is reformed. When the food supply is depleted around the area of the bivouac, the colony relocates.
Some colonies of army ants may number as high as one million individuals. Because of the spectacular size of their colonies and ‘raiding’ nature of these insects, they have been used repeatedly by the motion picture industry. Actually army ants pose no threat to humans or other large animals.
The authors recently had the opportunity to observe army ant behavior in Costa Rica. One morning we were walking down a dirt road with several students collecting insects. Collecting was not that good but suddenly hoards of insects, spiders and even a few scorpions and lizards started pouring out from the underbrush across the road we were on. After a few moments of excellent collecting, we decided to investigate the reason for this windfall. And, as you might suspect, there was a column of army ants moving through a gully to the side of the road. Of course all the animals in its path were attempting to flee. On the following evening a column of army ants raided the students' cabin. The students were not awakened, but the following morning they were very disappointed to see that the army ants had stolen most of the several thousand insects they had collected and mounted on pins over the past week. Shortly thereafter, I decided to test the reports that army ants pose no threat to humans. There was a column moving through our pension grounds--so I placed my foot directly in their path. They merely ignored this obstacle and marched over and around it.
While the army ants are primarily found in the New World tropics the driver ants are found in the tropics of Africa. Both types are very similar as far as their behavior and biology is concerned. One distinct difference is that while large colonies of army ants may number one million colonies of driver ants can reach 200 million. With such huge numbers they present more of a threat to humans and other animals. There have been human deaths recorded from the raids of these critters (mostly infants). In these cases death has typically occurred from suffocation as a result of the ants entering and filling the lungs.
The mating behavior of these ants is especially strange. The males are to drawn to the foraging columns supposedly looking for a mate. Instead of finding a queen the sterile workers quickly swarm the males and immediately tear their wings off. Then they carry them off and basically imprison them until a potential new queen is available.
Bullet Ants. This ant is primarily found in rainforests ranging from Nicaragua to Paraguay and Australia. This huge (1 inch) beast is called the bullet ant because its sting feels like being shot by a bullet. On the Schmidt Sting Index bullet ants rate as the number one most painful sting found in the arthropods. When defending their nest they swarm out, release a strong odor and stridulate an audible sound (said to sound like a shriek) and then grab and impale their intruder. In Central-South America they are referred to as the 24-hour ant, referring to the pain described as “of burning, throbbing, all consuming pain” that may last a day or more.
A one-inch Costa Rican bullet ant.
As with many other arthropods bullet ants play a ceremonial role in some tribes of the rainforests. The Satere-Mawe people of Brazil use this ant in the right of passage of boys into manhood. In this case live bullet ants are woven into a sleeve made of leaves with the stingers pointing inward. Once the sleeve is place on the arm the goal is to leave it on for 10 minutes without crying due to the stings. When finished the boys arms are temporarily paralyzed and they may shake uncontrollably for days. To fully complete the initiation, however, the boys must go through this ordeal a total of 20 times over a several month period or years.
Harvester Ants. These (Pogonomyrmex spp.) are commonly thought as the large red or black ants that form rather large nests in open fields, schoolyards, along railroad tracks, alleys or other similar situations. Of the 23 species that occur in the United States 22 occur west of the Mississippi River. Beside their large size and color these ants can be distinguished by fringes of long curved hairs on the back, underside margin of the head. These hairs are used to clean the ant’s antennae and legs, carry water and remove sand during excavation of their nests. The nests are typically quite large consisting of one or more holes surrounded by a low flat crater (up to 8 inches across). This crater in turn is surrounded by a rather large vegetation free area
A black harvester ant.
Harvester ants feed primarily on seed. In agricultural areas they are considered beneficial as they remove weed seeds from crops. The main reason they are found along railroad tracks is due the grain that is lost during transportation.
Harvester ants readily sting but typically are not aggressive unless defending the nest. If disturbed they will swarm from the nest and readily sting. Their venom is extremely powerful resulting in considerable pain that may last for several days. Harvester ant venom is the most toxic venom found in arthropods although there is considerably less than in black widows and consequently the sting of the ant is much less dangerous than the bite of the spider.
Fire Ants. There are many species of fire ants in the United States, but the most serious pests are 4 in the genus Solenopsis: the red imported fire ant, the black imported fire ant, the southern fire ant, and the fire ant. Distinguishing between imported and native species of fire ants is difficult, even for experts. Identification usually requires 40 or more randomly collected worker ants for study.
Black Imported Fire Ant. The black imported fire ant, Solenopsis richteri, is very similar to the red imported fire ant. Its current distribution is limited to a small area of northern Mississippi and Alabama. It may be displaced from established habitats by the red fire ant. Scientists have long thought that the black and red fire ants were 2 distinct species. Recently it has been discovered that hybrids of these ants produce viable offspring, and some scientists now wonder whether they are simply 2 races of the same species, varying in color and perhaps behavior.
Southern Fire Ant. The southern fire ant, Solenopsis xyloni, is a native species that occurs from North Carolina south to northern Florida, along the Gulf Coast and west to California. In California it occurs in the lower altitudes from Southern California up through Sacramento but is seldom found along the coast in central to northern California. This is probably our most common native species of ant but its distribution is greatly retarded when the Argentine ant is present. However in areas where the Argentine ant is controlled, populations of this species rapidly return.
Colonies may be observed as mounds or more commonly may be constructed under the cover of stones, boards, and other objects or at the base of plants. These ants also nest in wood or the masonry of houses, especially around heat sources such as fireplaces. Nests often consist of loose soil with many craters scattered over 2 to 4 square feet. In dry areas nests may be along streams, arroyos, and other shaded locations where soil moisture is high. Southern fire ants usually swarm in late spring or summer.
The workers are very sensitive to vibrations or jarring. If their nest is stepped on they will rush out and sting the feet and legs of the intruder. Individual reaction to their venom is quite variable depending on allergic reaction. There is a least one case of a human infant death due to mass stinging of this species.
This species is practically omnivorous feeding on a variety of materials including honeydew, meat, seeds, fruit, nuts, cereal and cereal products, grease and butter and dead and living insects. It can be quite detrimental to agriculture foraging for seeds from seed beds, girdling nursery stock, and consuming fruits and vegetables. In addition these ants will remove insulation from wiring and occasionally gnaws on a variety of fabrics.
Fire Ant. The fire ant, Solenopsis geminata, is a native species sometimes called the tropical fire ant. It ranges from South Carolina to Florida and west to Texas. It is very similar to the southern fire ant except its head is much larger and the petiole node is higher and narrower. This species usually nests in mounds constructed around clumps of vegetation, but may also nest under objects or in rotting wood.
Red Imported Fire Ant. The red and black imported fire ants were first reported in the United States in 1929. It is thought that they came to the port in some soil used as ballast in the bottom of a cargo ship. Since this introduction the black fire ant has not spread as rapidly as the red imported species. By 1953 (first official USDA survey) the red imported fire ant had spread to over 100 counties in 10 states. Today it is prevalent throughout the southeastern US and has moved into Texas, New Mexico. Arizona and California.
Natural movement of fire ants is limited to mating flight or by rafting during period of flooding. However, the rapid movement of these species across the South and westward is mainly associated with human activity. In this case the initial spread of these ants in the southeastern US was thought to be due to movement of sod and potted ornamental plants. This inadvertent movement of S. invicta and S. richteri was noted by the U.S. Department of Agriculture in 1953 when a direct link was established between commercial plant nurseries and the spread of imported fire ants. In response to mounting public pressure, the U.S. Congress appropriated $2.4 million in 1957 for control and eradication efforts. As part of an overall plan quarantine was imposed to retard or prevent the artificial dissemination of these now notorious pests. On May 6th 1958, regulations governing the movement of nursery stock, grass sod and some other items were instituted through the Federal Quarantine 301.81. By that time, however, imported fire ants had moved into 8 southern states. This spread, although slowed considerably by federal regulations and climatic conditions, continues even today. In recent years, isolated infestations of imported fire ants have been found as far west as New Mexico, Arizona California and as far north as Kansas and Maryland. In the case of California it is thought that the spread of these ants into this state was due to movement of bee hives as most initial infestations were found in around orchards and other situations where bees were moved into these areas for crop pollination. Based on USDA prediction these ants have a potential of even expanding the spread throughout much of the United States.
Current and potential distribution of imported red fire ant. Image courtesy of USDA.
Adult fire ants (Genus Solenopisis) are characterized by the presence of a ten-segmented antennae, two-segmented antennal club and two-segmented waste that joins the thorax to the abdomen which is typically darker than the rest of the body. Species identification is somewhat more difficult due to hybridization between the 2 "native" species as well as between the 2 imported species.
Diagram of diagnostic characteristics of red imported fire ant.
A mature colony of fire ants typically consists of 4 main stages: egg, larva, pupa, and adults. Since these are true social insect there is a caste system with different shaped and sized adults that carry out different function within the colony. These adult forms include the polymorphic workers, winged males, winged females and one or more reproductive queens. The egg, larval, and pupal stages (Figure 3) occur within the underground nest and are only seen when nests are disturbed or when they are being carried to a different location by workers (Figure 4). The eggs are small but can be seen with the unaided eye. They hatch into the grub-like legless larvae that are fed by the workers. Ant larvae in general are legless, carrot shaped with a well-developed unpigmented head capsule and are typically hooked at the head end. The larvae will grow and molt (shed their exoskeleton) 3 times prior to molting into the pupae, which are similar in appearance to the adults except that their legs and antennae are held tightly against the body. As with the larvae the pupae lack pigmentation, especially in the early instars. As they mature they begin to turn darker. As discussed in honeybees, the function of the polymorphic workers is determined primarily by age (and to a much lesser degree by size). Younger workers typically care for and feed the brood while middle-aged workers maintain and protect the colony. The oldest workers forage for food.
Figure 3. Egg, larval and pupal stage of fire ants. Image courtesy of USDA Archives.
Figure 4. Worker fire ants carrying larva for relocation. Image courtesy of USDA, Calif. Dept Agriculture.
The alates, or winged reproductives (Figure 5), are most abundant in the late spring and early summer, but can be found at any time of the year. The males are decidedly smaller than the females, glossy black and have a smaller head. Although both winged males and females can be found in the same colony, as a general rule one form will be dominant. It is possible that this functions to increase the chances of one sex mating with another from a different colony. Most colonies in a given area typically swarm on nuptial flights at the same time. This benefits the species and insures mixing of the gene pool. It is well-documented that inbreeding is generally detrimental to a given species.
Figure 5. A winged reproductive of the red imported fire ant. Image courtesy of USDA Archives.
Mating flights most often occur at mid-morning 1 or 2 days following a rainfall if the temperature is above 22°C and the wind is light. At this time a virgin female flies into a cloud of congregating males and mates in the air. The male subsequently dies while the female seeks a location to start a new colony. Once located, she breaks off her wings and excavates a brood chamber approximately 1 to 2 inches below ground. The new queen subsequently deposits a few dozen eggs which hatch in a little over a week. The queen does not forage but feeds the first generation of larvae from nutrients obtained from her fat reserves and by dissolving her no longer needed wing muscles. The larvae obtain the nutrients by trophollaxisis (exchange of alimentary fluids) or from sterile eggs she has produced for that purpose. The entire life cycle is completed in 3 to 4 weeks.
The initial generation of adult worker (minims) are relatively small due to a limited amount of nutrients available from the queen. Once developed these worker open up the brood chamber and begin to forage for available food. Soon another generation of larger adult workers has developed and the colony begins to grow. Workers start to emerge daily and within 6 months the colony population approaches several thousand and an above ground mound is visible. The polymorphic (poly in Latin means many and morph means form) nature of the worker becomes more apparent. The largest workers in the colony (majors) can be as much as 10 times the size of the smallest workers (media). The queen lives up to 7 years and produces an average of 1600 eggs per day. At maturity, a monogynous (one queen) fire ant colony can consist of over 250,000 ants. As discussed above some fire ant colonies have only one queen per nest while others can have many queens and are called polygynous colonies. The polygynous colony may be more difficult to control because all the queens must be killed to prevent the colony from surviving. Polygynous colonies frequently expand by "budding"; i.e., some of the queens and workers break off from the parent colony and start a new mound nearby. This process in polygynous colonies can accounts for much higher mound density which sometimes approaching 1,000 mounds per acre.
Different sized worker adults. Image courtesy of USDA Archives.
One of the identifying characteristics of an imported red fire ant colony is the earthen nest or mound. This mound is a cone-shaped dome with a hard crust. They averages 1 ½ feet in diameter and 8-inches in height. In heavy clay soils they can exceed 3-feet in height and 4 1/2 feet diameter. There are usually no external openings in the mound; but tunnels a few inches below the surface tunnels radiate several feet from the mound allowing foraging workers access to the colony. These mounds serves several functions: They act as a flight platform for nuptial flights and to raise the colony above ground in excessively wet soil while protecting it above ground from intruders and rain. They also serve as a passive solar collector to supply warmth to the colony during the cold winter months.
Mound of red imported fire ant. Image courtesy of USDA Archives.
In areas with hot, dry summers these mounds may not be maintained or may not be formed at all. In a dark, protected site with sufficient moisture and an adequate supply of food, fire ants will nest in a wide variety of locations (e.g. rotten logs, walls of buildings, under sidewalks and roads, in automobiles, in dried cow manure).
Fire ants are omnivorous, feeding on almost any plant or animal material; although dead and living insects seem to be their preferred food. In rural habitats, they have a major impact on ground nesting animals (birds, reptiles, mammals). Studies have shown that once established in a new area there is typically a minimum of a two-fold reduction in the populations of field mice, snakes, turtles and other vertebrates and a maximum of a total elimination of some species. Fire ants also feed on plants attacking young saplings and seedlings, destroying buds and developing fruits and have been shown to feed on the seeds of over a hundred species of native wildflowers and grasses.
Damage to plants is increased during periods of drought as fire ants
seek alternate water sources. In fields where drip irrigation is used, these
insects build their mounds over the emitters reducing or blocking the flow of
water to crops. In some cases, actual physical destruction of microsprinkler
assemblies has occurred. Finally, the mere presence of fire ants on plants and
within the field will deter hand-harvesting of crops.
As an urban pest, imported fire ants cause many of the same problems experienced in rural areas. In addition they nest within the walls of homes and offices. Colonies are established under sidewalks and roadways frequently resulting in complete collapse of sections of these structures if the nests are eventually abandoned. The presence of fire ants can deter outdoor activities in yards, parks and school grounds. Home invasions can threaten small children and the elderly. House invasions are especially prevalent during periods of heavy precipitation and flooding. Fire ant colonies have been found inside automobiles, trucks and recreation vehicles resulting in traffic accidents caused by fire ants stinging the drivers. Imported fire ants are attracted by electrical currents and have caused considerable damage to heat pumps, air conditioners, telephone junction boxes, transformers, traffic lights, and gasoline pumps.
Because of their reputation people fear fire ants. In some areas playgrounds, parks, and picnic areas are rarely used because of the presence of fire ants. In campsites of state and national parks in fire ant infested areas, it is often difficult to put up or take down a tent without being stung by angry ants.
Stings. Fire ants are best known for their behavior of stinging, frequently in mass. If a nest is disturbed hundreds if not thousands of ants will quickly emerge and attack the intruder. This occurs so quickly and in mass that is not uncommon to have hundreds on the victim before the first sting is felt. To make matters even worse a single fire ant can sting repeatedly and will continue to do so even after their venom sac has been depleted. Once reaching the victim the ant will typically attach with its mandibles to the skin and then insert its stinger. Subsequently it will rotate it abdomen and repeatedly sting using the attached head as a pivot. The result is a circle of several stings from the same ant.
Initially, the sting(s) result in a localized intense burning sensation (hence the name "fire" ant). Within a day or two a white pustule forms at the sting site (Figure 8). Pustule formation occurs only with the red and black imported fire ant and not the southern fire ant or fire ant. There is a possibility of secondary infection and scarring if the wounds are not kept clean or if they are continually picked at or scratched (Figure 9). As with any other hymenopterous stings, there are a few individuals who are hypersensitive to the venom and can react quite strongly and be severely affected. Symptoms in these cases can include chest pains, nausea, dizziness, shock or, in rare cases, lapsing into coma. In cases of an allergic reaction, even a single sting can lead to a potentially serious condition called anaphylactic shock. There are recorded cases of human death resulting from fire ant stings but these are rare.
Pustular formation for sting of red imported fire ant. Image courtesy of USDA Archives.
Figure 9. Secondary infection of sting from red imported fire ant. Image courtesy of USDA Archives.
Individuals with disabilities, reduced feeling in their feet and legs or reduced mobility, are at greater risk from serious stinging incidents and the incidence of resulting medical problems may be even greater. Large numbers of ants can sting and even overcome victims before they can safely escape. There was a recent case where fire ants entered a room of an elderly gentleman in a retirement hospital and basically stung him to death. In his case he was unable to escape their attack.
Individuals who are known to be allergic to fire ant stings should seek professional advice from a physician or allergist, especially if they are in situations where they might be exposed to these pests. There are emergency treatment kits that are available (by prescription) for individuals who are sensitive to their sting. Fortunately, relatively few deaths from fire ant stings have been documented, especially when compared to deaths from bee and wasp stings. Victims stung to death by fire ants often were not able to escape, sustained large numbers of stings, and suffered allergic reactions to the venom.
There are basically two methods of fire ant control, namely individual mound treatment and broadcast treatment. Before attempting either, it is advisable to check with regulatory agencies as the availability and use of different chemicals for either method may vary from state to state. In addition, in many cases free control by state governmental agencies of these pests is available.
Individual Mound Treatments. Treating individual fire ant mounds can be time consuming, but it is generally the most effective method of control. Once treated it will take anywhere from a few hours to a few weeks before total elimination of a colony depending on the product used, time of the year and size of the mound. Treatment is usually most effective in the spring with the key being to treat all the mounds in the area. If control is not complete, reinfestation of an area can take place in less than a year. There are several different methods that can be used to treat individual mounds.
Insecticides-One of the more commonly used methods is drenching mounds with a high volume of diluted contact pesticide. As with any treatment, it is extremely important to follow label directions not only to attain maximum effect, but to maximize safety of the application and avoid potential illegal consequences. In most cases the mounds and surrounding areas are wetted thoroughly but gently with the drench. Subsequently the mound is broken open and the insecticide is poured directly into the tunnels. Mound drenches are most effective after rains when the ground is wet and the ants have moved up into the drier soil in the mound. During excessively dry weather, effectiveness of the treatment may be enhanced by soaking the soil around the mound with water before treatment. One problem with this technique is that the queen may be too deep to be reached with the drench. This may be especially true if the colony is disturbed prior to an application. In this case the workers may move the queen deeper into the colony in order to avoid a potential threat.
Granular formulations are also available for individual mound treatment. In this case once the recommend dose is applied to the mound it should be watered thoroughly in order to reach the worker ants and queen that occur deeper in the colony. The dissolved granules must come into direct contact with the ants to have any effect. As in mound drenches, care must be taken not to disturb the colony prior to application.
A few insecticides are marketed as injectants. In
this case they may be injected using a "termite rig" with a
soil injector tip, a standard 1-3 gallon compressed air sprayer with a fire
ant injector tip, or a special aerosol soil injector system. The mound is injected
in a circular pattern, usually at 3 to 10 points. A new product combines
insecticide treatment with high temperature vapors to increase
Fumigants are readily available in most states for fire ant control. These are usually more effective than surface applications or mound drenches but are also more expensive and can be dangerous if not handled properly.
Depending on the state a number of fire ant baits are available. These can be used for treating individual mounds or for broadcast treatment of larger areas. The bait should be uniformly applied around the mound 0.3 to 1.0 meters away and not on the mound itself. Baits are much slower acting than the control methods listed above but are generally safer, cheaper and more effective in the long run.
Water - The use of
boiling water has been examined on several different occasions resulting in
varying degrees of success. In one experiment over a 50% of treated mound were
eliminated by pouring approximately 3 gallon of hot water directly into the
mound. The use of steam produced by a
steam generator produced similar results.
Regardless both techniques are far less effective the use of drenches,
fumigants, granular formulation or baits are
cumbersome in the field are not practical when dealing with large
populations of these pests. Area wide flooding with water has not proven to be
effective, impractical in most situations and can led to spreading of the
population due to the rafting ability of these insects.
Broadcast Treatments - A number of fire ant baits (Figure 10) are commercially available for broadcast treatments (again depending on the state). Baits are composed of an inert carrier-attractant (corn carrier and soybean oil) and toxicant. The active ingredient (either a slow-acting insecticide or an insect growth regulator) is incorporated into the oil. These baits can be applied either by a hand operated granular fertilizer spreader or larger equipment. Once foragers find bait they carry it back to the nest, ingest it and begin feeding other ants in the nest. Because the active ingredients are slow acting, they are spread around the nest before the desired effect. This formulation and means of application has a number of advantages. Unlike individual mound treatments, colonies need not be "located" in order for them to be treated and as a result this method is less time intensive and consequently less expensive than individual mound treatments. On the other hand broad cast treatment has the potential of affecting non-target organisms. It is also slow acting and the effectiveness of the bait is greatly reduced when they come in contact with water from rain, irrigation or other sources. Finally baits are only effective during those times of the year or temperatures when the ants are readily foraging. Generally speaking it is advisable to only use this type of treatment in areas where there is little or no human traffic. If broadcast treatment is used in such an area, a good choice is growth regulator bait, which poses much less risks to non-target species. For example, fenoxycarb bait has been shown to be very effective for suppression of fire ant populations when applied in one application over a wide area.
Figure 10. A corn- based bait used for control of the red imported fire ant. Image courtesy of USDA Archives.
Figure 11. A tractor driven granular applicator. Image courtesy of USDA Archives.