Stenotothorax schneppi Skelley and McPeak 2018, new species
Creators: name: Skelley, Paul E.
name: McPeak, Ron H.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Aphodiidae
Stenotothorax
Stenotothorax schneppi

description: Stenotothorax schneppi Skelley and McPeak, new species
Figures 2, 66–71
Diagnosis. Stenotothorax schneppi is distinguished from other members of the genus by the following combination of characters: protibia with secondary setal row, clypeus with 4 or more teeth and setal fringe, pronotal basal line and bead reduced, elytral striae wider and sharply edged at base, and elytra lacking lateral fringe of setae, small body size (<6 mm length). Stenotothorax schneppi appears to be restricted to the western part of the Snake River Plain in eastern Oregon and southwestern Idaho.
Description. Holotype male length 5.4 mm, width 2.4 mm. Body somewhat hour-glass shaped, widest at apical third of elytra; color nearly black, surface glossy. Head with clypeus narrow, distance between anterior most point of clypeal marginless than distance from teeth to frontoclypeal suture; clypeus anterior margin spiniformly dentate, with 2 primary teeth, 2 smaller teeth medially along the median emargination, one distinct smaller tooth lateral of the primary teeth followed by strong tooth-like crenulations toward the frontal lobes; clypeal margin with setal fringe present, but short in dorsal view; clypeal surface rugosely granulate on apical half, reducing in intensity towards the frontoclypeal suture, where it is weakly granulate; extreme anterior clypeal surface with few short indistinct setae; punctation of head distinct, fine, dense, evenly distributed from clypeus to vertex; frontal lobe projecting, angulate. Epipharynx with apical margin weakly sinuate, tylus projecting; chaetopedia few and stout; epitorma broad (Fig. 70). Pronotum posteriorly hemispherical in shape, widest anteriorly, constricted in basal half; surface near anterior angles not explanate; disc punctation two sizes, fine punctures evenly distributed, coarse 3× larger than fine punctures evenly widely scattered, separated by 4 or more diameters; lateral margin with short setal fringe along anterior half, evenly arcuate from anterior angles to middle of base, marginal groove and bead weak on basal half, posterior angles obliterated; basal margin evenly rounded, with fine marginal groove and bead only at middle, groove and bead absent on either side. Scutellum triangular, coarsely punctate basally, impunctate apically. Elytra fused, oval; each humerus reduced, humeral denticle absent; striae distinct, strial sides not crenated; striae I–V attaining base, VI nearly attaining base, I–VI sharply edged and weakly wider at base; strial punctures fine; interval punctation fine, arranged in two vague rows, surface weakly convex; epipleural fold lacking setae along lateral margin, a few setae present at base only. Appendages with hind wing vestigial, strap-like. Profemur with few indistinct coarse punctures on ventral surface. Protibia elongate, primary dorsal setal row situated along midline of surface; with a secondary row of setae; ventral surface lacking groups of coarse punctures; protibia lacking ventral projections at medial apex beneath spur and along medial basal margin; spur evenly curved inwardly. Meso- and metafemur finely punctate on ventral surface, few coarse punctures less distinct than profemur; of similar shape, elongate. Meso- and metatibia gradually widening before abruptly dilated apex. Meso- and metatibial spurs narrowed, saber-like; lower mesotibial spur 1/2–3/4 length of upper spur. Meso- and metatarsomere I length = length of upper spur. Venter with metasternum short; laterally punctures not evident only seta present, surface alutaceous, densely finely punctate medially. Abdomen with basal sternite setose and rugose across surface; medial and apical sternite surfaces as basal sternite laterally, smooth and setose medially. Male genitalia with parameres shorter than basal piece; sharply angled ventrally at apical third to acutely pointed apex in lateral view (Fig. 71).
Sexual dimorphism. No sexual dimorphism was noted.
Variation. Length 4.7–5.8 mm, width 2.1–2.6 mm. Older specimens show typical signs of wear on protibial and clypeal teeth. Setae on the anterior clypeal surface are present, but short and indistinct, even on pristine specimens. Any older specimens lack these setae. Color varies from red-brown (teneral) to nearly black. Secondary clypeal teeth vary in number and size.
Type material. Holotype: “/ IDAHO: Payette Co., 2560 ft, 4 mi. S of New Plymouth, Exit 9 on I-84 jct. St-30, 11-12-NOV-2014, P. Skelley, K. Schnepp, G. Powell / N 43°54′24” W116°48′59”, mouths of rodent burrows excavated by badgers / [red paper] HOLOTYPE Stenotothorax schneppi Skelley&McPeak /” Deposited in the FSCA.
Allotype and paratypes (n = 212): IDAHO: Payette Co.: same data as holotype [allotype and 47 FSCA, 28 GSPC]; 4 mi. S of New Plymouth, 43°54.390′N, 116°48.959′W, 3700 ft, 13-XI-2014, Skelley & Schnepp [6 RMPC]; ~ 11 miles SE Ontario, 43°54′24.78″N, 116°49′01.42″W, 11-12-XI-2014, Kyle E. Schnepp, [same as type locality: 4 CMNC, 2 CNCI, 4 DCGC, 71 KESC, 4 NHML, 2 SEMC, 4 USNM, 4- OSJM, 4 RCWC, 4 WBWC, 4 WFBM].
OREGON: Malheur Co.: 11.5 km. SE Vale, T19S R45E S 25, 785 m, 25-IX-1983 to 12-XI-1983, William H. Clark, Mary H. Clark [1 OJSM]; Moores Hollow Road & Hwy. 84, 44°10.959′N, 117°08.121′W, 2531 ft, 14-X-2015 to 15-III-2016, R.H. McPeak [6 FSCA, 6 RMPC]; 6 mi. S. Vale, T19S, R45E, NE1/4, AW1/4, Sec. 20, 2700 ft, 19-III-1975, C. Maser [4 CSCA, 9 DCC, 1 LACM].
Observed habits. The majority of the type series was collected in sandy depressions with organic detritus at the mouths of ground squirrel burrows and badger diggings. As with other members of the pyriformis complex the strength of their association with small mammals vs. that of organic matter accumulations in isolated sandy substrates needs to be studied further. Other specimens have been collected in barrier pitfall traps.
Remarks. Stenotothorax schneppi is the smallest species of the pyriformis complex, readily distinguished from the others by the reduced setal fringe of the elytral and clypeal surfaces, and isolated distribution. It is also the only species of the pyriformis complex that is known outside of the Great Basin. One hypothesis to its isolated distribution is its ancestor was washed to the lower Snake River Plain by the Lake Bonneville flood. Of course, more work and evidence are needed to substantiate any origin hypotheses for the species covered in this manuscript. First, more survey work is needed throughout the region to locate populations to study.
Etymology. This species is named for Kyle Schnepp, friend and colleague, who first collected them on a joint expedition where we collected three of the new species described here.
description: Published as part of Skelley, Paul E. & McPeak, Ron H., 2018, New species of Stenotothorax Schmidt from the northwestern United States (Coleoptera: Scarabaeidae: Aphodiinae), pp. 1-31 in Insecta Mundi 681 on pages 28-30, DOI: 10.5281/zenodo.3715079