Scientists abuzz at wasp's anti-ant warfare

A parasitic wasp that employs a bizarre form of psychological warfare to foment strife and civil war in ants' nests has provided scientists with a potential new form of pest control.

A parasitic wasp that employs a bizarre form of psychological warfare to foment strife and civil war in ants' nests has provided scientists with a potential new form of pest control.

An international study has found that the wasp secretes a chemical cocktail that causes ants to fight viciously among themselves. A similar substance could be used in an environmentally-friendly ant powder.

Scientists discovered the wasp's aggression drug by studying how it diverted the attention of the ants long enough to slip into their nest and to attack a caterpillar that the ants unwittingly protected.

Some of the chemicals found in the cocktail are new to science, and they could form the basis of a new class of "psycho-active" pesticides that affect only targeted insects.

The research team, from the Centre of Ecology and Hydrology in Dorchester, the University of Southampton and the Japanese National Institute of Agrobiological Sciences in Tsukuba, said the chemicals made by the wasp were the most powerful anyone had found.

"No other known secretion enables an insect to immobilise up to 80 per cent of an ant colony," the scientists say in a paper published today in the journal Nature. "The strength and persistence of this reaction suggests that similar cocktails of long-chain hydrocarbons might provide an alternative to the use of poisons and repellents to control pest ants."

The work involved studying two endangered insects – the parasitic wasp, Ichneumon eumerus, and its host species, the caterpillar of the butterfly Maculinea rebeli, which is threatened with extinction.

The caterpillar is disguised as a larva of the ant Myrmica schencki, which protects the caterpillar as if it were one of its own larvae. However, to lay its egg inside the caterpillar, the wasp secretes its chemical cocktail to induce fighting among female worker ants guarding the nest.

The scientists believe that the chemicals act as a pheromone, an external hormone, causing a severe change in behaviour that is quickly passed on from one ant to another. "The ants themselves amplify a sense of panic after contact with the wasp, creating a chain reaction of in-fighting across their society."