t 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 reduction