Ants Pawns In Battle Of Wasps, Butterflies

Ben Harder
National Geographic News
May 30, 2002

Even when they win, they lose. Hapless ants, like mortals caught in a crossfire between competing gods, are exploited in turn by two other insects—a butterfly and a wasp. When the wasp attacks the larval butterfly, it drives the ants to attack each other, turning them into incidental casualties.

The ants, researchers have discovered, are manipulated by chemicals produced by both sides in the struggle. Now scientists are wondering whether humans can use the wasp's powerful chemical cocktail as a non-toxic form of insect control. The research is reported in the May 30 issue of the journal Nature.

The highly sophisticated chemical warfare that has evolved between the Ichneumon eumerus wasp and Maculinea rebeli butterfly in western Europe has resulted in Myrmica schencki ants being used as pawns.

The ants are duped by chemicals into accepting, nurturing, and protecting the butterfly caterpillar as one of their own. But when the wasp detects a caterpillar hiding inside an ant colony, it uses its own clever chemical trickery to sow confusion in the ranks of the ants, allowing it to gain access to the caterpillar.

The intruding wasp, by secreting a cocktail of compounds called pheromones, throws the ants into such a frenzy that they attack and even kill one another. In the chaos, the wasp slips unnoticed through the ant nest and preys on the unguarded caterpillar.

If the chemicals can be synthesized and mass-produced, they could replace the poisons and toxic repellants currently used in ant traps, researchers say.

Pheromones have long been [considered for] use in controlling ants, said Graham W. Elmes of the Natural Environmental Research Council's Centre for Ecology and Hydrology in Dorset, U.K. New pheromones he and his colleagues in Britain and Japan have recently discovered last longer than most such chemicals, making them particularly promising candidates for insect control.

Time could be running out, however. In recent years, the endangered wasps that produce the chemicals have been found in just four alpine meadows—two in southern France, two in northern Spain. None of the sites are protected from agricultural development.

A Cast of Critters

Elmes describes the Myrmica ant as "a rather splendid beast" with large antennae that make it slightly resemble a minute stag. The ants live in highly complex, underground nests hidden beneath inconspicuous openings.

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