Cremastocheilus quadratus

One of about thirty-five species of myrmecophilous Cremastocheilus. The host ant may be Veromessor pergandei.

Identification
As indicated in the description, this insect is most nearly related to Cremastocheilus westwoodi, to which the student would be led by attempting to identify it by Horn's table of the genus. It differs markedly from that and other allied species, however, by the thorax not being narrowed behind; the pronotum is also more coarsely and less closely punctured toward the middle, the erect hairs are here more truly scales, the pygidium is more coarsely punctured, the tibia less stout, the front tarsi shorter and the mentum more deeply concave. The peculiar concave compression of the tarsal joints is not closely approached by any other species know to me. (Fall, 1912)

Distribution
Arizona, California

Habitat
Common ant host may be Veromessor pergandei.

Nomenclature
Described from three specimens sent by Mr. Junius Henderson, of the University of Colorado, who took them at Ft. Mojave on the Colorado River in Western Arizona, 16 March, 1911.

Description
Black, subopaque, above with very sparse short brownish erect or suberect hairs which become on the pronotal disk distinctly squamiform, varying from tow to three times as long as wide; hairs beneath sparse and very short, stiff and setiform. Mentum deeply and regularly cupuliform, the margin entire. Head as in Cremastocheilus schaumii and Cremastocheilus westwoodi. Prothorax nearly one-half wider than long, widest across the hind angles which are not at all retracted, sides very broadly and just visibly sinuate before the hind angles, arcuately narrowed in front, the apex 3/5 as wide as the base; front angles foveate, hind angles rectangular, triangularly smooth above, not limited within by an impression; disk broadly convex, median line impressed, punctures coarse and shallow, dense at sides, well separated toward the middle. Elytra moderately flattened, rather more so than in westwoodi, sculpture as in the latter species. Pygidium coarsely cribrate punctate. Body beneath coarsely moderately closely punctate. Tibiae distinctly less broad than in westwoodi; front tarsi short, passing the apex of the tibiae by only the terminal joint, or slightly more; middle tarsi subequal in length to the tibiae; hind tarsi a little shorter than the tibiae. All the tarsal joints are concavely compressed laterally, more strongly so basally, so that when viewed from above the joints appear much narrower at base. Length 12.5-14 mm; width 5-5.8 mm.