BioEd Online

Using a home-made trap, a tiny species of ant is capable of ensnaring prey much larger than itself and tearing it to pieces.

The ants (Allomerus decemarticulatus), which live in Amazonian plants called Hirtella physophora, construct a honeycomb-like structure out of their host plant's fibres from which they can stage an ambush.

The worker ants hide in the holes of this death trap with their mouths open wide, waiting for locusts, butterflies or other insects to land. When prey arrives they quickly seize its extremities, pulling on legs, arms and antennae until the hostage is rendered immobile. Once trapped, other ants from the colony arrive to sting and bite the prey until it is paralyzed ( see video).

"This is the first time we have seen ants capable of building a trap to ambush and capture prey," says researcher Jérôme Orivel from the University of Toulouse, France, whose report is published in this week's Nature¹.

"The prey are paralyzed and stretched very quickly, but after this initial capture the process becomes slow," says Orivel. "The prey is either cut into pieces or moved as a whole to where the ants are living." They then feed the bits of protein to their young.

The ants, studied in French Guiana, also farm a certain fungus on their host plant. Researchers believe the fungus is transported from plant to plant by the colony's queen. The mould is spread on top of the ants' trap to reinforce its structure, as it hardens into a fibreglass-like material. "The fact that they manipulate fungus to build the trap is also exciting," says Orivel.

Orivel's team says it has recently discovered that another, similar species of ants, Allomerus octoarticulatus, is capable of performing the same trick, although their traps seem to be smaller. He plans to study this species next.