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

by Thomas Lincoln Casey

Homalotusa Csy.

This subgenus, composed of rather large species with long and not much incrassated antennæ, in which the outer joints are more or less elongate, the eleventh much shorter than the two preceding combined, the mesosternal process extending almost to the middle of the coxæ and very acute, the metasternal projection very short and broadly angulated, the coxæ contiguous, the abdomen parallel and devoid of evident sexual modification, may be placed near Liogluta. The following are some additional species:

Atheta (Homalotusa) lanei n. sp.—Unusually stout, piceous-black, the abdomen black, legs pale, the antennæ fuscous; pubescence distinct but not dense, rather pale, very sparse on the abdomen; lustre shining; head transversely orbicular, the strongly setose eyes not very prominent, at their own length from the base; antennæ extending to the middle of the elytra, the tenth joint slightly elongate; prothorax nearly a third wider than long, much wider than the head and correspondingly narrower than the elytra, parallel, with rounded sides, rather convex, minutely, sparsely punctulate but flattened and with closer granuliform punctures medially toward base, with a short transverse impression just before the base; elytra large, slightly wider than long, very much wider and longer than the prothorax, impressed on the suture basally, rather closely, granularly punctate; abdomen slightly narrower than the elytra, remotely punctulate, the fifth tergite fully as short as the fourth and feebly trapezoidal. Length 3.2 mm.; width 0.92 mm. Oregon (Lane Co.).

Quite distinct from any other species in its much stouter form, short fifth ventral and many other features.

Atheta (Homalotusa) oregonia n. sp.—Moderately stout, black, the elytra dark brown, the abdominal tip slightly pale, the legs and antennæ as in lanei; pubescence finer and more abundant, the lustre duller throughout; head relatively larger, convex, moderately shining, the eyes smaller, at a little more than their own length from the base; antennæ long, scarcely incrassate, the tenth joint feebly obtrapezoidal and not quite so long as wide; prothorax formed as in lanei but smaller, a fourth wider than the head and more evidently narrower than the elytra, the parallel sides evenly rounded; surface evenly and feebly convex, the basal impression obsolete, the punctulation very fine and indistinct; elytra large, slightly transverse, not quite parallel, the humeri much exposed at base, the surface strongly micro-reticulate, the fine punctuation thereby rendered indistinct; abdomen wide, but little narrower than the elytra, with parallel and nearly straight sides to the tip of the fifth segment, not very closely, minutely punctulate throughout, the sixth tergite (♂) broadly sinuato-truncate at apex. Length 3.6 mm.; width 0.83 mm. Oregon (Lane Co.).

Allied rather closely to fuscula Csy., from Cœur d’Alene, but with relatively larger head and smaller and more transverse prothorax; the sex of the type is not altogether certain as announced above.

Atheta (Homalotusa) mormon n. sp.—Form more slender, black throughout, the elytra and legs piceous-black, the lustre strongly shining though distinctly micro-reticulate, the punctures minute, feebly and very indistinctly granuliform as in the preceding; pubescence rather sparce; head convex, parallel, the eyes at their own length from the base; antennæ very slender, the second joint much longer than the third, the tenth distinctively longer than wide; prothorax about a fourth wider than long, much wider than the head and narrower than the elytra, apparently a little narrower at apex than at base, the sides broadly arcuate; surface rather convex, shining, the transverse impression at the base very short and subobsolete; elytra large, slightly transverse, very much wider and longer than the prothorax, the straight sides feebly diverging from base to apex, the surface nearly flat, shining; abdomen rather wide, parallel, the fifth tergite distinctly longer than the fourth, the sixth rounded in the type. Length 3.2 mm.; width 0.78 mm. Utah (southwestern),—Weidt.

Not closely allied to any other species but belonging to the same subgenus as the preceding, as shown by sternal and general structure.

Atheta (Homalotusa) lacustrina n. sp.—Rather stout, more parallel than usual, feebly shining and pubescent, the abdomen more shining and with sparser vestiture; black or piceous-black, the legs bright, the elytra darker, rufous, the latter feebly blackish basally; antennæ dark, paler basally; head parallel, convex, rather shining, the eyes at their own length from the base, not very convex; antennæ long and slender, the tenth joint much longer than wide; prothorax large, very much wider than the head and only a little narrower than the elytra, fully a fourth wider than long, the sides parallel, broadly arcuate; surface finely, closely punctulate and with a small nearly rounded feeble impression near the base; elytra subparallel, much wider than long, the suture only a little longer than the prothorax, the surface feebly convex, finely, closely and inconspicuously punctulate, abdomen wide, slightly narrower than the elytra, parallel, minutely, not closely punctulate, the sixth tergite broadly arcuate, becoming gradually feebly sinuate medially at tip in the type, the sixth ventral broadly angulate, the angle rounded. Length 3.3 mm.; width 0.8 mm. Wisconsin (Bayfield),—Wickham.

Differs from any other described species of the subgenus in its more parallel and rather convex form.

Atheta (Homalotusa) wisconsinica n. sp.—More slender and less parallel than the preceding, piceous, the abdomen black, gradually bright rufous apically; elytra and legs pale brownish-rufous, the former infumate basally toward the scutellum, the antennæ fuscous, paler very gradually basally; head small, orbicular, the eyes at nearly their own length from the base; antennæ long, very slender, the second joint a little longer than the third, the tenth very distinctly elongated; prothorax not quite a fourth wider than long, parallel, with broadly and very moderately acuate sides, much wider than the head and correspondingly narrower than the elytra, minutely, closely punctulate, the basal impression very feeble; elytra parallel, wider than long, the suture distinctly longer than the prothorax, the slightly rough punctulation very minute and close-set; abdomen only moderately wide, much narrower than the elytra, minutely, sparsely punctulate, shining and unusually flat, the fifth tergite very much longer than the fourth, the sixth broadly and very evenly arcuate at apex in the type, and behind this, another segment, the surface of which is covered sparsely with stiff inclined spinuliform hairs; sixth ventral moderately narrow, with the apex arcuato-truncate. Length 3.5 mm.; width 0.75 mm. Wisconsin (Bayfield).—Wickham.

This distinct species differs greatly from the preceding in the more elongate fifth tergite, which in lacustrina is only about as long as the fourth; also in smaller prothorax, narrower abdomen, larger eyes and other characters. The sex of the type is not evident.