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

by Thomas Lincoln Casey

Microdota Rey.

The following species seem to be sufficiently allied in general organization to Microdota amicula Steph., to be included in the same subgeneric group, at least for the present:

Atheta (Microdota) alamedana n. sp.—Slightly shining, the reticulation distinct, coarse but feeble on the abdomen; punctures fine, not very close, slightly asperate on the elytra, the pubescence short, not dense; color black or faintly piceous, the elytra brown, the legs pale; head slightly wider than long, parallel, the eyes rather convex, well developed, as long and as prominent as the tempora, the carinæ fine, far from entire; antennæ short, distinctly incrassate, the outer joints mutually similar in form and transverse, the last gradually pointed, barely as long as the two preceding, the second as long as the next two combined; prothorax moderately transverse, much wider than the head and distinctly narrower than the elytra, parallel, feebly arcuate at the sides, the basal angles obtuse but distinct, only slightly blunt, the basal impression feeble, rounded; elytra not quite parallel, evidently shorter than wide, much longer than the prothorax, the apices not sinuate laterally; abdomen rather short, narrower than the elytra, parallel with feebly arcuate sides, the tergites subequal, the fifth (♂) truncate and coarsely but not strongly crenate, the sixth ventral semicircularly rounded; mesosternum extending but little beyond the middle of the coxæ, the apex finely aciculate, rather far removed from the moderate and angulate metasternal projection, the connecting subdepressed ridge narrowly and strongly convex. Length 1.6 mm.; width 0.38 mm. California (Alameda Co.).

A rather obscure species, agreeing in most of its characters with amicula.

Atheta (Microdota) saturata n. sp.—Blackish-piceous, the abdomen black, the elytra scarcely paler than the prothorax, the legs piceous; punctures very fine, the pubescence short, not dense, inconspicuous; surface moderately shining, the reticulation feeble, coarse but feeble on the abdomen; head slightly wider than long, wider basally, the eyes but slightly convex and shorter than the much more prominent and rounded tempora, the cairnæ wholly wanting; antennæ dark brown, moderately short, gradually distinctly incrassate, the ninth joint transverse, a little shorter than the tenth, the last gradually acute, rather longer than the two preceding, the second elongate, only a little longer than the third; prothorax as in the preceding but with the basal angles less evident and except in being only a little wider than the decidedly larger head, though more evidently narrower than the elytra, the latter larger, more transverse, much longer as well as wider than the prothorax, not evidently sinuate at the apices; abdomen much narrower than the elytra, subparallel, the fifth tergite much longer than the fourth, the sixth ventral in the type rather produced, with its apex broadly and circularly rounded; first four joints of the hind tarsi equal. Length 1.85 mm.; width 0.4 mm. California (Lake Tahoe).

Very distinct from the preceding in its antennæ, absence of cephalic carinæ and other characters.

Atheta (Microdota) ficta n. sp.—Piceous, the head and abdomen black, the legs pale piceous; surface slightly shining, the reticulation somewhat coarse but not strong, moderate and feeble on the abdomen, where it is transversely disposed posteriorly, the punctures fine, not dense, the vestiture rather coarse; head nearly as long as wide, the eyes well developed, rather convex, only a little shorter and just visibly less prominent than the tempora; antennæ fuscous, moderately incrassate, rather short, the outer joints mutually similar, transverse, the last obtusely ogival, barely as long as the two preceding, the second longer than the third; prothorax nearly as in alamedana in form and relationship with the head and elytra, but with the basal angles less evident, the impression obsolete; elytra rather large, shorter than wide, much longer than the prothorax, the apices not sinuate; abdomen rather wide though evidently narrower than the elytra, short, parallel, with feebly arcuate sides, the tergites equal; sterna nearly as in alamedana, except that the metasternum is much shorter and broader, broadly parabolic; basal joint of the hind tarsi longer, thicker and darker in color than two to four, which are equal. Length 1.6 mm.; width 0.42 mm. California (San Mateo),—Baker.

The general form and coloration of this species is not unlike alamedana, but the tarsi are of peculiar structure and the metasternal projection quite different.

Atheta (Nemota) properans n. sp.—Dark and uniform piceous-brown, the abdomen more blackish, alutaceous in lustre, finely and densely punctulate, the abdomen with the coarse reticulation almost obsolete, its surface polished and with numerous asperulate punctules; pubescence abundant, short, dark ashy; head well developed, rather transverse, broadening basally, the eyes rather convex and less prominent though barely as long as the tempora, the carinæ fine, far from entire; antennæ short but rather slender, dark brown, only very feebly incrassate, the outer joints but slightly transverse, the last rather obtuse, the second longer than the third, though much shorter than the next two combined; prothorax moderately transverse, much wider than the head and correspondingly much narrower than the elytra, the parallel sides somewhat strongly, evenly arcuate, the basal angles obtuse and blunt but rather evident; basal impression small, rounded, feeble though clearly defined; elytra moderately transverse, much longer than the prothorax, the apices distinctly sinuate externally; abdomen much narrower than the elytra, feebly narrowing and with nearly straight sides throughout; hind tarsi and sterna nearly as in alamedana but with the basal joint of the former sensibly shorter than the second. Length 1.85 mm.; width 0.42 mm. California (Hydesville, Valley of Eel River, Humboldt Co.).

Distinct from any of the preceding in lustre, sculpture and situation of the elytral apices.

Atheta (Nemota) repens n. sp.—Rather more elongate than any of the preceding, slightly shining, the reticulation fine but distinct, feeble and somewhat transversely disposed on the still more shining abdomen, the punctures very fine, not dense, slightly close and feebly asperulate on the elytra, very sparse and feeble on the abdomen; color blackish-piceous, the head and abdomen black, the elytra a little paler though rather dark piceous, the legs blackish-piceous; head wider than long, parallel, the eyes moderately convex, as long and about as prominent as the tempora, the carinæ extending to about the middle, fine; antennæ rather short, gradually and distinctly incrassate, the outer joints moderately transverse, the last obtuse, shorter than the two preceding, the second much longer than the third but shorter than the next two; prothorax moderately transverse, somewhat wider subapically than basally, with feebly arcuate sides, distinctly wider than the head and rather evidently narrower than the elytral base, the median line finely impressed in basal half; elytra subparallel, only slightly shorter than wider, very much longer than the prothorax, the apices not sinuate laterally; abdomen rather long, much narrower than the elytra though slightly wider at the apex of the fourth tergite than at base, the sixth ventral in the type feebly produced, broadly trapezoidal, with the apex arcuately truncate and the angles broadly rounded. Length 1.9 mm.; width 0.42 mm. California (Truckee).

The sterna of this distinct species are nearly as in alamedana, except that the metasternal projection is much shorter and more broadly though evidently angulate; the tarsi are rather slender, with the first four joints of the posterior equal.

Atheta (Microdota) perversa n. sp.—Form rather stout and a little larger, black, the elytra dark piceous, the legs pale piceo-flavate; surface slightly shining, closely and very finely punctate and micro-reticulate, the reticulation of the abdomen coarser but almost completely obsolete, its surface polished; pubescence short, rather abundant, dusky-cinereous; head slightly transverse, sensibly broader basally, the eyes about as long as the tempora but less prominent, the carinæ fine, extending to the middle; antennæ pale brown, moderately short and incrassate, the outer joints evidently wider than long, the last elongate-oval, nearly as long as the two preceding, the basal joints as in the preceding; prothorax very moderately transverse, parallel, with rather feebly rounded sides, much wider than the head and evidently though less markedly narrower than the elytra, vaguely flattened or subimpressed medially; elytra moderately transverse; much longer than the prothorax, the apices distinctly though not deeply sinuate externally; abdomen distinctly narrower than the elytra, the sides feebly converging and straight from base to apex, finely, rather closely and evidently punctate, the sixth tergite in the types small, with the apex feebly sinuate medially, the angles broadly rounded; sterna nearly as in the preceding, except that the apex of the mesosternum is less aciculate, being very narrowly truncate at tip, the tarsi similar. Length 2.0 mm.; width 0.52 mm. California (Gualala, Mendocino Co.).

In the peculiar form and sculpture of the abdomen this species resembles properans, but otherwise it is quite different.