About Polyergus mexicanus
Polyergus mexicanus shows some physical variation across its distribution range, with an average total length of 6 millimetres (0.24 in). Individuals from the southern part of its range have glossy heads, while those from eastern and northern populations have more matte heads. The dorsal surface of the mesonotum is matte, and the lateral sides of the mesonotum are usually shining. The gaster is also shining, but this shine is partially hidden by a layer of short erect hairs, most noticeably on the dorsal surface of the gaster. Its body is generally red, with the posterior portion of the tergites tinged brown. The legs may be slightly darker than the body, and the hairs on its dorsal surface are grey — these hairs are never yellowish, which distinguishes this species from P. breviceps. This species also has longer brownish macrosetae (thicker, longer hairs), but these often wear away, leaving dark scars on the tergites. Polyergus mexicanus is the most widely distributed species in the genus Polyergus in North America. It is native to western Canada and the United States, the U.S. states of North Dakota, South Dakota, and Arkansas, and Mexico. It most commonly lives in open woodland with little undergrowth, or in mixed woodland and grassland habitats. In the southern part of its range, it is only found at higher altitudes: it occurs at 2,200 metres (7,200 ft) in the Chiricahua Mountains of Mexico, and at 2,800 metres (9,200 ft) in Chihuahua, Mexico, typically growing in open coniferous forests there.
