Pogonomyrmex

Pogonomyrmex is a genus of harvester ants, occurring primarily in the deserts of North and South America. The genus name originated from the Greek language and refers to a beard-like structure, the psammophore, below the head (gr. pogon = beard), which can be found in most species of the subgenus sensu stricto. The psammophore are used for gathering small seeds, helping to increase the efficiency of transportation of fine sand and pebbles during nest construction, or to carry eggs. However, this structure is missing in species of the subgenus Ephebomyrmex (gr. ephebos = beardless lad): these species generally have smaller individuals and colonies.

Pogonomyrmex sensu stricto workers have the most toxic venom documented in any insects, with Pogonomyrmex maricopa being the most toxic tested thus far. It has an LD50 of only 0.12 mg/kg, compared to honeybee venom, at 2.8 mg/kg, and comparable to cobra venom (there are, in fact, only about a dozen recorded LD50 values for snakes which are lower than 0.12, mostly seasnakes). This venom is presumed to be an anti-vertebrate defense, specifically against predators that have evolved to selectively feed on them, most notably horned lizards. Note, however, that the actual amount injected by a single ant is incredibly small, and they pose no actual threat to humans or other animals. Also note that very few insects have had the toxicity of their venoms formally tested, and it is likely that other insects have more potent venoms (e.g., the venom of Lonomia, which can kill humans).

These ants dig very deep nests with many underground chambers in which they keep seeds, from which they derive food for their larvae. The areas around most Pogonomyrmex sensu stricto nests tend to be utterly devoid of vegetation, and are easily seen from a distance. In addition to horned lizards, there are predatory wasps in the genus Clypeadon which feed only on Pogonomyrmex workers, paralyzing them with their venom, and then carrying them back to a burrow where they will serve as food for the wasp's larva.