Cremastocheilus opaculus

One of about thirty-five species of myrmecophilous Cremastocheilus. The host ant is presumed to be a species in the genus Myrmecocystus.

Key to Trinodia species
Closely allied to Cremastocheilus spinifer, but with the disc of thorax more sharply divided and differently sculptured. The hind angles of the thorax are not everted. It is also allied to Cremastocheilus planipes, but that has broad thin tibiae. (Horn, 1894) Clypeus strongly carinate at middle; elytra with punctures in the form of elongate scratches; trichome hairs on eye ridge (canthus) and in depression centrad of anterior posterior angles.

Distribution
Arizona (Coconino Co., Black Point, 3 km S. Grey Mountain, G.Alpert), California, Nevada, Utah, and Mexico.

Nomenclature
Type Material: Baja California. Pescadero, no date; described by Horn (1894).

Description
Oblong, black, opaque, dorsum very flat. Clypeus strongly carinate at middle. Disc of thorax sharply divided into three regions, anterior angles auriulate, the posterior spiniform, sides arcuate, sinuately narrowing to the hind angles, base sinuate within the angles, disc coarsely punctured, the outer lobes more coarsely and closely, the central portion more sparsely and more opaque. Elytra flat with punctures in the form of elongate scratches on the disc, but decidedly punctiform at the sides. Body beneath shining with coarse sparse punctures. Legs slender. Mentum entire. Length, .44 inch; 11 mm. (Horn, 1894)