Cremastocheilus retractus

One of about forty-five species of myrmecophilous Cremastocheilus. The host ant is Formica.

Identification
Body black, not shining above; foveae inside of the anterior angles with tufts of trichome hairs on each side, small shallow notch on inside of angle; posterior angles suddenly and strongly retracted, surrounded by a groove; elytra with large shallow punctures, open behind; pygidium with apical surface smooth, polished; body hairs thick basally, becoming pointed apically.

Distribution
Arkansas (1.7 km N of Fort Douglas, Johnson County, April 27, 2009, Colorado (Cherry Creek SP, Arapahoe County, March 31, 2010), Illinois (Mason Co.), Iowa (Des Moines Co., Lee Co.), Kansas, Nebraska, Texas (Travis Co.), Wyoming; Canada (Manitoba); Mexico (Durango)

Habitat
Common host is Formica. Spruce Woods Prov. Park, Manitoba, Canada, April 25, 2015, in sand dune habitat.

Biology
Formica gnava is reported as the host ant from Travis County, Austin, Texas (Wheeler, 1908)

Nomenclature
Texas; Mr. Belfrage. One specimen, no date (MCZ). The mentum is deeply and broadly incised behind. This species is allied to Cremastocheilus canaliculatus, but the prothorax is more convex, the foveae adjacent to the front angles do not extend to the apical margin and the hind angles are much retracted, so that the base is fully one-fourth narrower than the middle of the prothorax, as in Cremastocheilus variolosus, to which it in other respects has no resemblance. (LeConte, 1874)
 * Cremastocheilus walshi Westwood 1874 Syn.
 * Cremastocheilus incisus Casey 1915 Syn

Description
Brownish-black, not shining; prothorax wider than long, coarsely punctured, narrowed in front, broadly rounded on the sides, foveate inside of the front angles, foveae not extending to the apical margin, hind angles suddenly and strongly retracted, acute, surrounded by a deep groove; elytra flattened, with the usual sculpture of large shallow punctures, not closely placed. Length .44 inch; 11 mm.(LeConte, 1874).