

Few adapatations are more convenient than tricking other creatures into caring for your young. Most adept at this bit of foolery is the cuckoo bird, which lays its eggs in other birds' nests; but no less spectacular is the Alcon blue butterfly, which hoodwinks ants into caring for its larvae.

In a study published yesterday in Science, University of Copenhagen entomologists describe how Alcon caterpillars secrete chemicals similar to those used by local ants to communicate. Ants adopt Alcons after finding them newly hatched from eggs laid on leaves, then nurture them for up to two years while their own young go untended. Ant colonies can protect themselves by evolving a different smell, but such progress is lost during interbreeding with colonies who haven't developed a similar defense.

If that particular cycle of life leaves you a little less warm and fuzzy than butterflies usually do – or, conversely, makes you marvel at the ingenuity of evolution – then read on: the Alcon blue has a nemesis, the Ichneumon eumerus wasp. When the wasp detects an Alcon caterpillar inside an ant colony, it charges inside and sprays a pheromone cocktail that makes the ants attack each other. The wasp slips through the confusion, lays its eggs inside the caterpillar and leaves. After the caterpillar turns into a chrysalis, the eggs hatch and consume the it from the inside.

National Geographic once described the ants involved as being "like mortals caught in a crossfire between competing Gods." Sadly, these particular Gods are vanishing: both the Alcon blue butterfly and *I. eumerus *are endangered.

Smell-wars between butterflies and ants [press release]

A Mosaic of Chemical Coevolution in a Large Blue Butterfly [Science]

Image: University of Copenhagen, Jeremy Thomas

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