Florida's skull-collecting ant, next to trap-jaw ant body parts

The ant species Formica archboldi keeps the skull-like head capsules of its prey after squirting victims with a powerful acid. Credit: Adrian Smith

Zoology

Skull-collecting ants slay with acid

A potent chemical allows ants to slaughter larger prey.

Like the caves of ogres in fairy tales, the nests of the Formica archboldi ant are littered with the ‘skulls’ of their prey: ants in the Odontomachus category. But how the head-hunting ants kill their victims has been a mystery. Odontomachus ants are larger than their predators, and seemingly fiercer; their common name, trap-jaw ants, alludes to their wickedly effective spring-loaded jaws.

Now, Adrian Smith at the North Carolina Museum of Natural Sciences in Raleigh has discovered how F. archboldi take down trap-jaws. Smith collected ants of both species from around Florida and analysed the chemical waxes that coat their bodies. He also filmed combat between the species to try to work out the attack strategies used by the skull-collecting ants.

He found that the chemical odours of the two species are nearly identical — a tactic that, he suggests, might allow F. archboldi to disguise itself among its prey. The attacking ants then paralyse their victims using a precisely delivered stream of formic acid.