#gatekeeper ant

Also known as Exploding Ants, from those species that can fatally burst their own gaster to release alarm pheremones. They nest in wood, dead branches or galls, with an exit exactly as wide as the head of the major workers, who plug the entrance unless another worker wants in or out of the nest.

There are almost 100 species in the genus, which is widespread in Australasia, SE Asia, North America, and Europe.