In the meadows of Europe, colonies of industrious team-workers are being manipulated by a master slacker. The layabout in question is the Alcon blue butterfly (Maculinea alcon) a large and beautiful summer visitor. Its victims are two species of red ants, Myrmica rubra and Myrmica ruginodis.

The Alcon blue is a ‘brood parasite’ – the insect world’s equivalent of the cuckoo. David Nash and European colleagues found that its caterpillars are coated in chemicals that smell very similar to those used by the two species it uses as hosts. To ants, these chemicals are badges of identity and the caterpillars smell so familiar that the ants adopt them and raise them as their own. The more exacting