Hairy Chemists

A beetle uses chemical warfare in the fight for survival

Woe is the hungry insect that tries to dine on a squash beetle pupa. The bright yellow creature is easy enough to find and may appear defenseless, as it has no effective mechanical weaponry such as a mean bite. But suspended on the tips of its microscopic hairs are droplets of complex chemicals that can deter almost any predator. An ant that touches the hairs, for example, frantically cleans itself.

Cornell University chemists have been astonished to discover that the pupae use only three simple molecules to build a library of more than 1,000 defensive compounds.

The substances contain unusual rings built from very large numbers of atoms. "Because the chemicals are so diverse, predators may find it particularly difficult to evolve countermeasures," explains Cornell chemical ecologist Thomas Eisner. The beetle´s tactic of producing large numbers of closely related chemicals is also used by pharmaceutical chemists, who thought they had invented the process, which they call combinatorial chemistry.