Memoirs on the Coleoptera/Volume 1/New Species of the Staphylinid Tribe Myrmedoniini/Tribe Myrmidoniini/Group Athetæ/Atheta/Macroterma

by Thomas Lincoln Casey

Macroterma Csy.

This subgenus of Atheta is related to Stethusa and has the same very broad and apically arcuate process of the mesosternum, but it is here shorter and separated from the metasternum by a longer interval. The eyes are much smaller, being at nearly their own length from the base of the more parallel-sided head, the outer antennal joints much shorter and more transverse, with the last greatly elongate, being almost as long as the three preceding combined; the male sexual characters are materially different and more complex. Of the three described species, borealis Csy., is unfortunately founded upon the female, but it may be distinguished from alutacea Csy., by the more sparsely punctulate and puberulent and more polished integuments; dentata Bernh., has the head and prothorax relatively smaller and more transverse, with the protuberance of the fifth male tergite very much smaller and of different form. The following is another species:

Atheta (Macroterma) iowensis n. sp.—As small as dentata and relatively narrower and more parallel, the antennæ much larger, stouter and more incrassate, the eleventh joint less acutely pointed; black, the elytra and legs pale piceo-flavate; antennæ blackish throughout; head distinctly narrower than the prothorax, the eyes less prominent than in dentata; prothorax parallel, evenly rounded at the sides, finely punctuate and moderately pubescent; elytra large, slightly transverse, with feebly diverging sides, distinctly wider and very much longer than the prothorax; abdomen moderately narrow; parallel, the fifth tergite (♂) with a very small and sharply elevated tubercle close to the hind margin and more posterior in position than the somewhat similar tubercle of dentata, the sixth tergite with a slightly projecting and broadly arcuate apical lobe, about a third as wide as the basal width of the segment, the lobe with two short carinæ separated by a concavity at each side of its surface, the median part more arcuate and with a minute median sinus at apex, the segmental apex at each side of the lobe unevenly crenulate and wrinkled. Length 2.7 mm; width 0.7 mm. Iowa (Iowa City),—Wickham.

The specimens at hand are gummed alongside of a large black ant, having the pedunculated abdomen relatively very stout, but it is hardly assumable that the beetle and ant are associated very closely.