Deep in the forests of Borneo live species of ants with a rather novel way of fending off enemies: they explode.

While they were first identified in 1916, no new species have been discovered since 1935.

Now, a group of international scientists from multiple disciplines including botany, chemistry and entomology, have discovered 15 more separate species of these kamikaze ants.

Ants — found virtually everywhere on Earth — have complex social colonies that can contain millions of the tiny critters.

Like bees, their colonies have queens as well as workers and a brood of eggs or young ants. Typically, worker ants are larger than the others and work to protect and defend.

But not the Colobopsis explodens, a new species of Colobopsis cylindrica, known colloquially as "exploding ants," described in the journal ZooKeys.

When threatened, the ant raises up its posterior to warn off the potential enemy. If the offending threat — say, a researcher studying it — doesn't take the hint, the ant chomps down on itself, flexing so hard that its abdomen bursts with yellow, sticky, toxic goo.

This method of self-sacrifice is called "autothysis."

"They explode when attacked by an enemy (or poked with a finger)," lead researcher Alice Laciny, who is completing a PhD at the University of Vienna, told CBC News. "The composition of the goo is currently under investigation, but it certainly contains sticky and toxic components."

But these ants get even stranger.

While the "minor" workers partake in self-sacrifice, the major workers protect the colony by barricading the nests with their enlarged, gaping-mouthed heads.

In that way, the major ants are somewhat reminiscent of whale sharks, the giants of the oceans who feed by swimming with their mouths open. Perhaps not surprisingly, they're called the "doorkeepers."

A major worker of Colobopsis explodens, with its characteristically enlarged head. (Heinz Wiesbauer)

"The evolution of the explosion behaviour and the diverse body types of the castes are amazing," lead Laciny said.

Mysteries to solve

Rather than living below-ground, as many other species of ants do, these ants are found in the canopies of the forests, which was part of the research challenge all these decades.

But with special climbing equipment and expertise, co-author of the paper Alexey Kopchinsky was able to explore the trees, shedding light on these poorly understood species.

And, while the researchers are pleased to have discovered more species of these unique ants, there's still more to uncover.

Only now are they beginning to study these ants in better detail, which includes chemical, microbiological, behavioural and anatomical analyses.

The researchers have identified Colobopsis explodens in this new paper, but it will serve as model species as they continue to uncover more secrets about the ant once simply referred to as "Yellow Goo."