New type of “exploding ants” found in Borneo

Credits: Laciny A, Zettel H, Kopchinskiy A, Pretzer C, Pal A, Salim KA, Rahimi MJ, Hoenigsberger M, Lim L, Jaitrong W, Druzhinina IS (2018) / ZooKeys

When they are confronted by an enemy, the “exploding ants” of South East Asia do exactly what their name suggests: they explode. Undiscovered for decades, researchers have recently found over a dozen species that belong to this group, including one completely new species. 

Ants are capable of astonishing prosocial behaviour, such as the creation of bridges and life rafts, recovering injured ‘soldiers’ from the battle field during attacks on termites, and even the administration of medical treatment. But in terms of self-sacrifice, the “exploding ants” from the trees of South East Asia are leading the pack, ready to give up their lives to protect their colony. Confronted with a threat, these ants can deliberately rupture their own abdominal walls. This desperate measure releases a sticky toxic substance that can kill an opponent in hand-to-hand combat.

Scientists refer to this ability as “autothysis”, a suicidal behaviour that has also been documented in certain termites. Such is the lot of supercolonies. Contrary to individuals in the majority of species, who seek to preserve and reproduce their genes, ants and termites work for the sake of the whole colony; individual loss comes after the needs of the whole. Note that in ants, it is only the smallest worker ants, the minors, those who look after the domestic tasks inside the nest, who explode.

Scientists have known about explosive ants for over a hundred years. Several species were documented in the first half of the 20th century, and a new group of species called Colobopsis cylindrica was created in order to describe them. A recent expedition to Borneo, Thailand and Malaysia, led by an interdisciplinary team of researchers from the National History Museum in Vienna, the Technical University of Vienna and other contributing institutions, are now trying to change that.

The results of their enquiry, published in the journal ZooKeys, identified 15 distinct species of exploding ant, who were totally new to science, and have been baptised Colobopsis explodens. This species are particularly subject to exploding when they are under threat (some of them even exploded when the researchers got too close).

During the expedition, the researchers also observed mating while ants were in full flight. They additionally observed their feeding habits – apparently, these insects snack on algae, moss, mushrooms, dead insects, fruit and fish.