Pogonomyrmex maricopa and Novomessor albisetosa workers, fighting. Resources are scarce in the desert and competition among ants is fierce, leading to frequent conflicts. Green Valley, Arizona, USA
Two harvester ants 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 feisty little Argentine ant (Linepithema humile) attacks a much larger fire ant (Solenopsis invicta). Both species co-exist naturally in subtropical South America, but in the southern United States where both have been accidentally introduced, the fire ant has displaced the Argentine ants. Austin, Texas, USA
