They’ve Got High Hopes

Allomerus decemarticulatus is a tiny tree-dwelling ant which lives in the forests of the northern Amazon. Researchers examining the relationship between different ant species and their host plants noticed that this particular ant lived on only one plant - Hirtella physophora - and that they built galleries hanging under its stems.

Many ant species build these galleries as hideouts to act as sanctuaries between their nests and foraging areas. But the team, led by Jérôme Orivel at the University of Toulouse, France, spotted that A. decemarticulatus were using these galleries as traps for prey.

The traps are woven together using hairs stripped from the ants’ host plant and reinforced with fungus, producing a platform with pitted holes. “The ants are always hiding just under the holes, waiting with their mandibles open. When an insect arrives they immediately grab the legs and antennae,” says Orivel. This pulling immobilises the victim, stretching it out as though being tortured on a mediaeval rack.

Worker ants then clamber over their helpless prey, biting and stinging until the victim is paralysed or dead. The carcass is then chopped into small pieces while still on the rack or, more likely, carried back to the leaf pouch to be devoured. The surprise-attack traps are “like something out of Edgar Allan Poe”, says Mike Kaspari, an ant expert at the University of Oklahoma, US.