 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 a