 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.
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