Cremastocheilus beameri

One of about thirty-five species of myrmecophilous Cremastocheilus. The host ant is Camponotus ocreatus.

Identification
Cremastocheilus beameri most closely resembles Cremastocheilus planatus from which it can, however, be distinguished by its smaller size and narrower form. In C. beameri the dorsal surface of the fourth anterior tarsal segment is much shorter than the ventral surface of that segment, whereas, in C. planatus the two surfaces are subequal. Also in C. beameri the third segment of the anterior tarsus is attached to the fourth below the upper proximal corner. In C. planatus the third segment is attached to the fourth at the proximal dorsal corner. The anterior tarsi of C. beameri resemble those of C. puncticollis except that the fifth sement is laterally flattened basally in the former and not in C. puncticollis. It can be further separated from C. puncticollis by its large and dense pronotal and elytral punctures. In C. puncticollis the pronotum has sparse, small punctures and the elytra are nearly impunctate but with occasional irregular scratches.

Distribution
Arizona (Douglas, San Bernardino Ranch, 3750ft., August, F.H. Snow), (Pima Co., 11 Sept. 1914, Mark Robinson)

Habitat
Common host is Camponotus ocreatus.

Biology
Found emerging from the nest of Camponotus ocreatus in August. After emergence from the ant host nest, beetles mate at the entrance to kangaroo rat and other mammal burrows. Location for larval development is unknown.

Description
Medium sized,, robust, black. Head with vertex moderately punctate, punctures separated by about their own widths, front with larger nearly confluent punctures, lateral carinae extending along the inner margins of eyes prominent, median rounded carina extending to clypeal margin, base of head with deep transverse impression; canthus relatevely inconspicuous, sparsely clothed with short pile; clypeus reflexed, slightly emarginate at middle above carina, unequal to width of head at eyes; mentum cupuliform, shallow, anterior margin evenly rounded, sides subangulate, posterior margin produced at middle into prominent point; antennae ten-segmented, scape large, dorsal surface shallowly  convex. Pronotum four-fifths as wide as elytra at base, side margins evenly rounded anteriorly, nearly straight at base, widest at apcial third, basal and apical angles noduliform, anterior median impression shallow, posterior impression rather deep; disk with shallow, longitudinal, median impression, surface irregularly punctate, punctures generally separated by about one-half their own widths, open areas often present, laterally more densely punctate. Elytra widest at humeral angles, side margins slightly sinuate behind umbone, subparrallel to apical sixth then evenly rounded to apex, disk concave, sides rather sharply elevated, large subcylindrical ring-like punctures densely covering surface, often coalescent; scutellum extending to about basal third, sharply pointed posteriorly, sparsely covered with lunate impressions; meso-episternum not flattened above. Beneath rather densely covered with lunate impressions, sparsely pilose; legs long, compressed, anterior tibiae bidentate apically, fourth segment of anterior tarsus with upper surface only one-third as long as ventral surface, third segment attached to fourth below upper proximal corner; pygidium subcylindrical, punctures separated by about one-third their own diameters, median carina prominent. Length 13 mm., width 5 mm.