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

by Thomas Lincoln Casey

Traumœcia Rey.

I have applied this subgeneric name to a few species which resemble Atheta in all essential structural characters, but are of very small size and rather slender form.

Atheta (Traumœcia) ithacana n. sp.—Dark piceous, the head and abdomen blackish, the elytra dark piceous-brown, the legs pale; surface rather shining, the micro-reticulation moderate, stronger on the elytra, the punctures very fine, asperulate and close on the elytra; head moderately transverse, the eyes rather large and more prominent than the tempora, which are shorter, parallel and straight to the rounded basal angles; carinæ fine, feeble, not quite entire; antennæ extending to the middle of the elytra, rather thin, the outer joints moderately transverse, the last as long as the two preceding, the second long, cylindric, the third much shorter, obconic; prothorax moderately transverse, distinctly wider than the head and narrower than the elytra, parallel but only feebly arcuate at the sides, finely impressed along the median line; elytra but slightly wider than long, much longer than the prothorax; abdomen much narrower that the elytra, parallel, very slightly narrowing apically, the fifth tergite much longer than the fourth, the sixth feebly and gradually sinuate medially at tip in the type; mesosternal process extending slightly behind the middle of the coxæ, gradually and finely pointed, separated by a considerable interval from the rather short but broadly angulate metasternum, the depressed intermediate ridge rather convex; hind tarsi somewhat elongate, with the first four joints subequal. Length 1.8 mm.; width 0.45 mm. New York (Ithaca).

Readily distinguishable by the form of the head and antennal characters.

Atheta (Traumœcia) orbiceps n. sp.—A little larger than the preceding, still more blackish throughout, the elytra very dark piceous-brown, the legs pale, the antennæ as in ithacana dark piceous, paler basally; pubescence a little longer; head slightly smaller, more orbicular, but slightly wider than long, the tempora behind the large eyes converging and more rounded to the base; carinæ similar, the antennæ nearly similar, the outer joints only very moderately transverse, nearly as in ithacana but relatively somewhat larger, much wider than the head, not impressed along the median line; elytra similarly slightly wider and much longer than the prothorax, scarcely more distinctly wider than long and subparallel; abdomen longer, more parallel, not narrowed apically, the sides nearly straight, the fifth tergite much longer than the fourth, the sixth as in the preceding but broader; sterna as in ithacana, the obtusely angulate metasternal projection somewhat blunter, the tarsi similar. Length 2.1 mm.; width 0.45 mm. Iowa (Cedar Rapids),—Brendel.

Closely allied to the preceding but differing in the form and size of the head, smaller terminal joint of the antennæ, more parallel abdomen and other features.

Atheta (Traumœcia) subdola n. sp.—General form, coloration and sculpture as in the preceding but more slender and with a notably smaller prothorax, rather more shining; head and antennæ similar; prothorax moderately transverse, parallel but more strongly rounded at the sides, very moderately wider than the head though much narrower than the elytra, very obsoletely impressed along the median line; elytra but little wider than long, very much longer than the prothorax; abdomen as in orbiceps; sterna similar, the mesosternal process not quite so finely pointed and the metasternal projection rather more sharply angulate; hind tarsi similarly slender, with the first four joints equal. Length 2.0 mm.; width 0.42 mm. Wisconsin (Bayfield),—Wickham.

In general organization the three preceding species agree very well, and they form a perfectly natural group, whether or not actually the same as the European Traumœcia, as represented by a specimen before me named T. ravilla Er.

The following species is aberrant in its more strongly asperate sculpture:

Atheta (Traumœcia) asperiola n. sp.—Subparallel, very moderately convex, scarcely shining, distinctly micro-reticulate, the punctures fine and close, strongly asperulate, the vestiture short; dark piceous, the head and abdomen black, the elytra rather dark and uniform brown-flavate, the legs pale; head moderately transverse, the eyes longer and more prominent than the tempora, which are parallel, rounding basally, the carinæ very fine, not entire; antennæ rather short, much thicker and more strongly incrassate distally than in the three preceding, the outer joints strongly transverse, the last stout, oval, pointed, rather longer than the two preceding, the second and third elongate, equal; prothorax transverse, distinctly wider than the head and narrower than the elytra, the parallel sides moderately arcuate, rather more so before the middle than basally, scarcely impressed; elytra distinctly transverse though much longer than the prothorax; abdomen parallel throughout, narrower than the elytra, the fifth tergite but slightly longer than the fourth, the sixth in the type broad, very feebly and gradually sinuato-truncate medially at tip' mesosternal process extending to nearly apical fourth of the coxæ, gradually prolonged but only moderately slender at apex, well separated from the short and broadly angulate, rather blunt metasternum, the intervening ridge very broadly convex; hind tarsi with the joints moderately slender, the first but slightly shorter than the second. Length 2.3 mm.; width 0.5 mm. New York (Catskill Mts.).

This species resembles the preceding in the tarsi, sterna and carinæ of the head, but differs in sculpture and in the sculpture of the antennæ.