Not all of the thorns on a swollen-thorn Acacia house the ants' larvae, but those that do are heavily guarded. Here, Pseudomyrmex spinicola patrol a nest entrance, ready to use their stings if the photographer approaches too close. Chiriqui, Panama.

Pseudomyrmex pallidus Tucson, Arizona, USA

Pseudomyrmex apache. Ants of the genus Pseudomyrmex inhabit pre-existing cavities in wood and vegetation, in this case an old wood-boring beetle burrow. Tucson, Arizona, USA