Chemical Weapons and Suicide Bombers: The Wonderful World of Insect War

Researchers from Imperial College London have discovered that aphids fight off predators with a deadly chemical attack. The insects release a pungent mustard oil bomb to ward off its enemies, mostly ladybirds, and to protect the colony.

aphids by environmental graffiti, a UK based environmental blog

The aphids, which feed on cabbages, consume chemicals called glucosinolates. These chemicals are stored in the blood and are reacted with the enzyme myrosinase to produce the mustard oil explosion. The defence technique is usually a suicide mission, as the reaction almost always kills the aphid as well, but preserves the aphid colony.

Only wingless aphids use this mechanism, whilst those that grow wings quickly loose the glucosinolates, presumably as they can just fly away instead.