Western harvester ants (Pogonomyrmex occidentalis) make distinctive mound nests on the desert floor. Hallelujah Junction, California, USA

Two harvester ants (Pogonomyrmex rugosus) from adjacent nests engaging in ritual warfare, pushing in a display of force but not actually harming each other. It is thought that colonies use these mock battles to gather information about their neighbors. Knowledge about the strength of competing colonies helps ants set territorial borders without loss of life. Tucson, Arizona, USA

A Pogonomyrmex rugosus worker shows off her psammophore, the basket of long hairs on the underside of her head used for carrying sand grains. This structure enticed Austrian taxonomist Gustav Mayr to name this genus Pogonomyrmex, or "bearded ant". Tucson, Arizona, USA