Memoirs on the Coleoptera/Volume 1/New Species of the Staphylinid Tribe Myrmedoniini/Tribe Myrmidoniini/Group Athetæ/Atheta/Stethusa
Atheta Thoms.
Stethusa n. subgen.
If Dr. Bernhauer had examined the under surface of his Atheta klimschi, which he assigns to typical Atheta, he would probably have observed that in the sternal structure it bears very little resemblance to the true Atheta, where the mesosternal projection between the coxæ is more or less prolonged and slender to aciculate. In this subgeneric group the sterna between the coxæ are notably wide, the mesosternal process only extending to slightly beyond the middle of the coxæ, with its apex transversely to circularly rounded and separated from the angular apex of the metasternal projection by a short and slightly depressed interval. This section of Atheta includes numerous species in North America, the following being some of the many allies of klimschi:
| Atheta (Stethusa) affluens n. sp.—Stout, parallel, moderately convex, blackish-piceous, the elytra and legs pale, the former obscure flavate, the abdomen black, scarcely paler apically; anterior parts moderately shining, minutely, closely punctuate and finely, closely, and inconspicuously pubescent; head four-fifths as wide as the prothorax, transversely orbicular, the eyes large; antennæ fuscous, pale at base, extending to the middle of the elytra, gradually moderately enlarged distally, the third joint slightly longer than the second, both elongate, the tenth slightly wider than long, the eleventh as long as the two preceding; prothorax two-fifths wider than long, nearly as wide as the elytra, parallel, the sides broadly arcuate, the median line very finely, almost imperceptibly impressed throughout; elytra a little wider and longer than the prothorax; abdomen more shining and more sparsely punctulate, a little narrower than the elytra, subparallel, the fifth tergite (♂) transversely truncate, unmodified, the sixth strongly arcuate at tip and acutely dentate at each side, the middle of the arc narrowly truncate, the truncature marked at each end by a very small convex knob and the surface adjoining feebly impressed. Length 2.7 mm.; width 0.7 mm. Rhode Island (Boston Neck) and New York (Long Island). |
Specimens not clearly separable from the considerable type series are before me from New Jersey (Anglesea), North Carolina (Asheville), Mississippi (Pass Christian) and Arkansas (Little Rock). It is a widely diffused species, readily distinguishable by its large convex eyes, extending almost to the base of the head, by the medial truncature of the sixth male ventral scarcely so wide as the distance separating it from the lateral slender teeth and not extending behind the latter, and by the sternal characters.
| Atheta (Stethusa) irvingi n. sp.—Form, coloration and sculpture nearly as in affluens, the head relatively larger but otherwise similar, fully five-sixths as wide as the prothroax, the latter even relatively larger than in affluens, similar, except that the parallel sides are slightly less rounded; antennæ with the last joint evidently shorter; elytra similar, but little wider than the prothorax and with the humeri only very narrowly exposed at base: abdomen less parallel, slightly narrowing near the apex, the fifth tergite (♂) similarly truncate and unmodified, the sixth with the apical arcuation larger, with smaller lateral teeth, the median truncature sinuate, with the adjacent surface more impressed and its ends not marked by swollen joints. Length 2.5 mm.; width 0.65 mm. New York (Catskill Mts.). |
Resembles affluens very much but distinguishable by the somewhat larger head, shorter last antennal joint and slight differences in the male sexual characters.
| Atheta (Stethusa) galvestonica n. sp.—General form, coloration and sculpture as in klimschi, the punctuation not quite so dense and the lustre more shining, the prothorax shorter, more transverse and paler in color; head well developed, the eyes large but separated from the base by fully two-fifths of their own length, the antennæ more slender, very moderately incrassate, with the outer joints nearly as long as wide; prothorax rather more than one-half wider than long, the basal impression feeble; elytra rather short and transverse, the suture not distinctly longer than the prothorax; abdomen as in klimschi; mesosternal process unusually broad, rounded at tip, which is separated from the triangular metasternal projection by but little more than its own subapical width. Length 2.3-2.5 mm.; width 0.65-0.7 mm. Texas (Galveston). |
Though represented at present by the female only, this species can be distinguished readily from any other by the very wide mesosternal process even for the present genus, and the eyes, which are not quite so large as usual.
| Atheta (Stethusa) texana n. sp.—Of the usual coloration and rather stout form, the head well developed, with the eyes not quite so large as usual and decidedly more prominent; antennæ rather rapidly though moderately incrassate, the outer joints evidently though not greatly wider than long; prothorax not densely punctate, strongly transverse, strongly rounded at the sides, nearly as wide as the elytra, feebly impressed medially except in apical third; elytra large, wider than long, with the suture much longer than the prothorax and similarly rather shining, with the distinct asperate punctures not very dense; abdomen as in klimschi and galvestonica; mesosternal process extending to apical fourth of the coxæ, moderately wide, rounded at tip and separated by only its own width from the large triangular metasternal projection. Length 2.6 mm.; width 0.75 mm. Texas (Austin). |
Also represented by the female but to be known readily by the more prominent eyes, which are decidedly smaller than usual, although much larger than in Atheta, and by the shorter and more transverse prothorax.
| Atheta (Stethusa) canonica n. sp.—Very similar throughout in form, coloration and sculpture to affluens but a little smaller and less stout, the head just visibly larger and with the similarly large eyes slightly less convex; prothorax almost similar but rather shorter, more impressed along the median line posteriorly; elytra similar but shorter, strongly transverse; abdomen with thinner and deeper side margins, paler basally and at apex, the sixth tergite (♂) with the truncate median part at apex not projecting behind the lateral teeth but very much wider than in affluens, being separated from each of the teeth by a space very much narrower than its own width, and having its apex feebly sinuato-truncate and its lateral limits marked by very obtusely rounded unthickened angulations. Length 2.4 mm.; width 0.6 mm. Rhode Island (Boston Neck). |
Distinguishable from affluens principally by the notably different sexual modification fo the sixth tergite of the male. Superficially, the species of this section of Atheta resemble each other very closely throughout.
| Atheta (Stethusa) sagax n. sp.—Smaller than any of the preceding and with relatively shorter prothorax and elytra, similar in coloration and sculpture; head rather more transverse, very much narrower than the prothorax, the large eyes similar, and, as usual, finely faceted and having a few stiff bristling setæ; antennæ rather less developed but of the same type, the last joint fully as long as the preceding tow, the latter each but little shorter than wide, prothorax nearly one-half wider than long, parallel and broadly rounded at the sides, evidently narrower than the elytra; the basal angles distinct as usual; elytra pale brownish-flavate, feebly clouded toward the scrutellum; the suture but little longer than the prothorax; abdomen blackish, faintly rufescent basally and at apex, the sixth tergite (♂) with the medial truncature not more posterior than the tips of the slender dentiform process at each side of the apex and separated therefrom by nearly its own width, its apex faintly sinuato-truncate and its subangulate ends rounded and not at all thickened. Length 2.2 mm.; width 0.58 mm. Virginia (Norfolk). |
Seperable from any of the preceding by its rather smaller head and prothorax and small size of the body, as well as by differences in the male sexual characters.
| Atheta (Stethusa) sororella n. sp.—More slender than any of the preceding species and rather smaller in size, similar in coloration and sculpture; head moderate, the eyes large, convex, extending almost to the base; antennæ well developed, the last joint as long as the two preceding; prothorax transverse, parallel, very much wider than the head and a little narrower than the elytra, the latter short and transverse, the suture is not longer than the prothorax; abdomen much narrower than the elytra, rather shining, sparsely punctuate as usual, the lateral margins scarcely at all elevated, the sixth tergite (♂) with the apical lobe not projecting beyond the lateral processes and very wide, subsinuate medially and with very widely rounded unthickened angles, separated from each slender lateral process by but little more than half of its own width. Length 2.5 mm.; width 0.56 mm. New York (Catskill Mts.). |
The slender form and broad, feebly defined lobe of the sixth male tergite will probably prove efficient determinative characters for this species.
| Atheta (Stethusa) subdebilis n. sp.—Moderately stout, small in size, colored as in the preceding species, the fine close sculpture also similar; head rather well developed, almost three-fourths as wide as the prothorax, the large eyes almost extruding to the base as usual, the antennæ moderately developed, with the penultimate joints slightly wider than long, the last barely as long as the two preceding; prothorax more nearly as wide as the elytra, moderately transverse, parallel with rounded sides but with the base more rounded than usual and with a small rounded discal foveola near the base; elytra very little wider than the prothorax, much longer than in any of the preceding the culture infuscate basally and much longer than the prothorax; abdomen shining, much narrower than the elytra, finely and not closely punctulate, evidently pubescent, the sixth tergite (♂) with the median truncate lobe about as wide as the interval between it and the lateral processes and limited at each side by a strong swelling of the surface, its median part concave; mesosternal process rather than usual, its truncate apex distant from the metasternum by but little more than its own apical width, the metasternal angulation much more rounded at tip than usual. Length 2.0 mm.; width 0.5 mm. Missouri (St. Louis). |
Departs rather radically from the preceding species in its longer elytra, which are however together about a third wider than long, and in recognizable differences in general form and sternal structure.
| Atheta (Stethusa) spuriella n. sp.—Moderately stout, testaceous, the head piceous, the elytra more flavate, the abdomen clouded posteriorly except at apex; sculpture minute and dense, sparse on the elytra; head transversely oval, the eyes not quite so large as usual, separated from the base by nearly two-fifths of their length; antennæ with the outer joints rather stout, decidedly wider than long, the last as long as the two preceding; prothorax as in subdebilis; head, prothorax and elytra increasing in even but gentle ratio in width, the last as in subdebilis; abdomen and sexual characters nearly as in that species, the swellings marking the median lobe of the sixth tergite (♂) continued forward for a rather greater distance as obtuse ridges; sterna nearly similar, the metasternal angle less rounded. Length 2.4 mm.; width 0.6 mm. New York (Catskill Mts.). |
This species and the preceding form a small group of Stethusa, distinguished by a less sharply angulate metasternal angle, not quite so large eyes, rather more transverse antennal joints, longer elytra and more pronounced apical characters of the sixth male tergite. Spuriella differs from subdebilis in its relatively larger head and larger and more incrassate antennæ, among the more obvious characters.
The following species is appended very doubtfully to this subgenus, as it differs markedly in general form and antennal structure, though having the very broad mesosternum:
| Atheta (Stethusa) mendosa n. sp.—Rather stout, moderately convex, not parallel, distinctly shining and very minutely, not closely punctulate, the punctures rather well separated even on the elytra, the abdomen polished, minutely, sparsely punctuate; blackish-piceous, the pronotum a little paler, the elytra still paler; legs and basal joint of the antennæ very pale; head well developed, the eyes convex, prominent, at nearly their own length from the base, the tempora arcuate and converging behind them, the carinæ distinct, entire; antennæ moderately long, rather rapidly and strongly incrassate distally, the second joint cylindric, the third obconic and a little longer, both very elongate, the outer joints distinctly transverse; prothorax relatively small, strongly transverse, parallel and strongly rounded at the sides, much wider than the head and correspondingly much narrower than the elytra, which are parallel, rather strongly transverse and much longer as well as wide then the prothorax; abdomen parallel, slightly narrower than the elytra, the fifth tergite slightly longer than the fourth; mesosternum extending beyond the middle of the coxæ, very wide between them and flat, with the apex broad and circularly rounded, approaching the apex of the larger triangular metatarsal projection by its own apical width, the angle of the metasternum rounded; hind tarsi slender, the four basal joints equal. Length 2.7 mm.; width 0.75 mm. Virginia (Fort Monroe). |
Though represented only by the female, this species is so distinct in its structural characters that it could not be mistaken; the male characters would probably decide whether it is to be properly associated with the other species of the subgenus or not; it is certainly remarkably different from them in general appearance and all characters except the very broad sterna.