Pogonomyrmex imberbiculus, one of North America's smallest Pogonomyrmex. Portal, Arizona, USA

One of the strangest recorded ant phenomena is a hybrid zone between two species of harvester ants in the western United States. Pogonomyrmex rugosus and Pogonomyrmex barbatus apparently hybridized in the ancient past, leading to a pair of genetically complex daughter lineages that continually need to cross with each other in order to make worker ants. The queens and males remain genetically separate. Young queens need to mate with their own species to produce more queens and males, and with the other species to produce workers. This image shows a hybrid worker leaving the nest. Portal, Arizona, USA

A film crew for a National Geographic documentary sets up a robotic camera on a nest of red harvester ants, Pogonomyrmex barbatus. Sycamore Canyon, Arizona, USA