Argentine ants, those aggressive unstoppable pests that invade homes and farms throughout California and many other states, live in peace and harmony with each other inside their enormous colonies, but scientists are finally discovering how to make those ants destroy their own relatives in spasms of chemical warfare.
In laboratory experiments, researchers have found that when they alter the chemical coding those common household ants carry on the skeletons outside their bodies, all hell breaks loose. The ants, unable to recognize their altered nest mates, will tear the strangers' legs apart, rip off their sensitive antennae and battle them to the death.
The research is only in its earliest stages, but the scientists who conducted the experiments say they could be on track to finding a method to wipe out the common Argentine ants without harming any other benign creatures that share their environment.
The key to the scientists' research is the unique chemicals the ants carry on the exoskeletons that cover their bodies. The chemicals enable the insects to recognize each other as genetically similar, but when researchers interfered with those recognition signals, the untreated ants became bitter enemies of the ants whose chemical coatings were altered.
"This is really important because the team is finally starting to crack the code of how Argentine ants recognize and communicate with each other, and we can think of ways that this information could be used to control the ants in the future," said Brian Fisher, chairman of entomology at the California Academy of Sciences in San Francisco, who is one of the world's leading experts on ants of all kinds and sizes, but is not a member of the research team.
Scientists believe the ancestors of the Argentine ants probably migrated to America from their native Argentina in the 1890s inside sacks of coffee shipped to Louisiana. Quickly spreading north and west, they attacked other ants and established dominance everywhere -- except in the southern states, where more aggressive fire ants have kept them at bay.
In California, the Argentines are common everywhere and truly dominant. A single colony now stretches for hundreds of miles, from south of San Diego to as far north as Ukiah in Mendocino County -- not in one single nest, but in an uninterrupted sequence of settlements. All the ants share a common genetic heritage, and many queens hold sway.
Pesticides don't seem to stop them, nor do efforts at trapping them, and they damage many crops and wipe out many more benign ant species.
The team of researchers tackling the problem from the University of California at Irvine includes organic chemist Kevin Shea, evolutionary biologist Neil Tsutsui, and Shea's graduate student, Robert Sulc, who reported on the group's successful findings Thursday at the annual meeting of the American Chemical Society in San Francisco.
The chemicals that naturally cover the ants and serve as "recognition clues" for their colony mates are long chains of hydrocarbons linked to methyl groups, and their waxy composition also helps keep the ants' bodies from drying out and prevents infection, according to Tsutsui.
In a series of carefully controlled experiments involving thousands of the Argentine ants, but using groups of 50 ants at a time, Sulc and Shea created a varied group of synthetic hydrocarbons in similar but slightly different forms from the "recognition chemicals" normally carried by all the Argentine ants in the colony.
"We've tried 80 to 100 different variants of the recognition chemicals that coat the exoskeletons of the ants," Tsutsui said in an interview, "and many of them really do disrupt their normal social behavior. Our experiments are only preliminary, but it could lead to the first effective way of controlling these invasive pests."
