Ants turn into suicide bombers

Scientists have discovered a new species of ant that boasts a remarkable defence mechanism. When threatened, it explodes, covering intruders with sticky, toxic liquid.

The species, formally known as Colobopsis explodens and nicknamed Yellow Goo, is not the first type of ant found to deploy the unusual but highly effective defence, but it is the first to be fully classified since 1935. It is described in the journal ZooKeys.

Exploding ants live in the rainforests of south-east Asia, and were first noted in 1916. Differentiating species has proved highly challenging, in part because the insects live in dense forest canopies where access is difficult, so until now they have all be lumped into a single, undifferentiated genus.

In 2014, researchers from Thailand, Brunei and Austria gathered together for the first ever interdisciplinary conference dedicated to the ants. By comparing notes, the scientists tentatively identified 15 species within the genus, and the slow, painstaking work of describing them began.

C. explodens is the first to see the light of day, in paper written by a team head by Alexey Kopchinskiy from the Technische Universitat Wien in Austria, and Alice Laciny of Vienna’s Natural History Museum.

The researchers report that not every member of the species goes bang. The behaviour is limited to a single caste, called minor workers, which the authors describe as “particularly prone to self-sacrifice”.

Other castes within the species also exhibit unusual behaviours, however. Major workers, for instance, have disproportionately large heads, which they use to plug nest entrances in order to barricade against invaders.