Stenotothorax wintoni Skelley and McPeak, 2018

Skelley, Paul E. & McPeak, Ron H., 2018, New species of Stenotothorax Schmidt from the northwestern United States (Coleoptera: Scarabaeidae: Aphodiinae), Insecta Mundi 681, pp. 1-31 : 16-18

Stenotothorax wintoni Skelley and McPeak , new species

Figures 1, 9 , 14–15 , 17, 21 , 42–47

Diagnosis. Stenotothorax wintoni is distinguished from other members of the genus by the following combination of characters: protibia with secondary setal row, head with clypeus broad, clypeus with setal fringe and spiniform teeth, pronotal basal groove and bead reduced, and pronotal surface near anterior angle weakly explanate. Stenotothorax wintoni appears to be restricted to the Snake River Valley.

Description. Holotype male length 7.4 mm, width 3.4 mm. Body elongate, somewhat hour-glass shaped; color dark red-brown to nearly black, glossy. Head with clypeus broad, distance between anterior most point of clypeal margin roughly equal to the distance from angle to frontoclypeal suture; clypeal anterior margin with spiniform tooth each side of middle, tooth situated medially of most anterior part of clypeal margin, margin weakly crenulate near teeth and with short setal fringe, distinct in dorsal view; clypeal surface rugose, granulate, and finely, distinctly punctate up to frontoclypeal suture; frons and vertex with fine, distinct, dense punctures; frontal lobe projecting, angulate. Epipharynx with apical margin sinuate, tylus projecting; chaetopedia few and stout; epitorma broad ( Fig. 46 ). Pronotum with sides and base hemispherically rounded, transverse, widest anteriorly, distinctly constricted in basal half, surface near anterior angles weakly explanate; disc punctation two sizes, fine punctures evenly distributed, dense, coarse punctures roughly 5× larger than fine punctures evenly widely scattered; lateral margins lacking setal fringe, evenly arcuate from anterior angles to middle of base, posterior angles obliterated; basal margin evenly rounded, with marginal groove and bead at middle fine, reduced to lacking on either side. Scutellum triangular, coarsely punctate basally, impunctate apically. Elytra fused, oval; each humerus reduced rounded, humeral denticle not evident; striae distinct, sharply edged, wider at base and over declivity; striae I–VI reaching base; strial punctures fine, not crenating strial sides; intervals weakly convex, flattened, punctation distinct, fine, arranged in vague rows, all intervals similarly punctate, glossy; epipleural fold setose at base only. Appendages with hind wing vestigial, strap-like. Profemur densely coarsely punctate on ventral surface. Protibia elongate, primary dorsal setal row situated along midline of surface; with a secondary row of setae; lacking ventral projections at medial apex beneath spur and along medial basal margin; protibia lacking coarse punctures on ventral surface; protibial spur evenly curved inwardly. Meso- and metafemur finely punctate on ventral surface, few coarse punctures less distinct than on profemur. Meso- and metatibia gradually widening before abruptly dilated apex. Meso- and metatibial spurs narrowed, saber-like; lower mesotibial spur weakly sexually dimorphic, curved in at apex, 1/3–1/2 length of upper spur. Meso- and metatarsomere I length = length of upper spur. Venter with metasternum short; laterally punctures not evident, seta present, surface alutaceous, sparsely finely punctate medially. Abdomen with basal sternite setose and rugose across surface; medial and apical sternite surfaces as basal sternite laterally, alutaceously glossy and glabrous medially. Male genitalia with parameres shorter than basal piece; angled ventrally at apical third to acutely pointed apex in lateral view ( Fig. 47 ).

Sexual dimorphism. Female lower mesotibial spur 1/2 length of upper spur, not modified. Sexes difficult to distinguish without dissection.

Variation. Length 6.3–7.5 mm, width 2.8–3.4 mm. All available specimens show little of the wear visible on other species. We suspect this is simply sampling bias. Some variation or wear was noted on the clypeal setal fringe. The development of the basal marginal groove and bead showed some variation in the amount of reduction on either side of the middle.

Type material. Holotype: “/ IDAHO: Owyhee Co., Bruneau Dunes SP, 42.90575, -115.68792, 23-NOV-15- DEC-2014, gopher burrow trap, P. Skelley, K. Schnepp, A. Gillogly, R. Winton / [red paper] HOLOTYPE Stenotothorax wintoni Skelley&McPeak /”. Deposited in the FSCA.

Allotype and paratypes (n = 98): IDAHO: Bonneville Co.: Idaho Falls, N.R.T.S., 17-IV-1967 [1 BYU] ; Elmore Co.: Bliss Dam Dunes , 42.91728°N, 115.08693°W, 4-II-17-III-2015, R. Winton, B. Lyon [3 FSCA] ; Owyhee Co.: same data as holotype [4 CMNC, 2 CNCI, 2 DCGC, allotype female and 50 FSCA, 2 NHML, 2 OJSM, 2 RCWC, 4 RMPC, 2 USNM, 2 WBWC] ; same locality, 42.90452°N, 115.68546°W, 23-XI-15-XII-2014, P. Skelley, K. Schnepp, A. Gillogly, R. Winton [2 FSCA] ; same locality, 15-XII-2014 to 4-II-2015, R. Winton, B. Lyon [1 FSCA] ; same locality, 42.90163°N, 115.68079°W, 15-XII-2014 to 4-II- 2015, R. Winton, B. Lyon [2 FSCA, 2 RCWC] ; same locality, 42.89940°N, 115.67979°W, 15-XII-2014 to 4-II-2015, R. Winton, B. Lyon [1 FSCA] ; same locality, 42.90124°N, 115.68006°W, 23-XI-15-XII-2014, P. Skelley, K. Schnepp, A. Gillogly, R. Winton [4 FSCA] ; same locality, 23-XI-2014, K.E. Schnepp [2 KESC] ; same locality, 42°45′21″N, 115°41′17″W, 2510 ft, 23-XI-2014, P. Skelley, K. Schnepp, A. Gillogly, R. Winton, [7 FSCA, 1 KESC] .

Observed habits. Most available specimens were collected in Thomomys burrows, while the first specimens were collected nocturnally, dispersing on the dunes near these burrows in near freezing temperatures. Another couple were collected in barrier pitfall traps.

Remarks. Stenotothorax wintoni is most similar to S. washtucna and S. woodleyi , differing from both of these by their lack of clypeal teeth.

Etymology. This species is named for Ross Winton, Idaho Department of Fish and Game, who assisted with our initial collection of this species on the Bruneau Dunes and is continuing survey work for other Stenotothorax in Idaho.

Figures

Figures 1–9. Stenotothorax spp. characters. 1–2) Extreme age-related wear on Stenotothorax spp.; note lack of clypeal teeth, smoothing and dulling of clypeal surface granulations, and reduction of protibiae. 1) S. wintoni. 2) S. schneppi. 3) Deformity on a S. woodleyi, note apparent tubercle is not centered on head. 4–9) Stenotothorax species heads. 4) S. niviviator. 5) S. odontomonteus. 6) S. nevadensis (Nevada, Washoe Co., Washoe Lake). 7) S. winnemucca. 8) S. lahontanensis, narrow head. 9) S. wintoni, broad head.

Figures 10–15. Stenotothorax spp. characters. 10–14) Stenotothorax pronotal and elytral bases. 10) S. niviviator, complete pronotal marginal bead, rounded strial margin. 11) S. odontomonteus, reduced pronotal marginal bead, rounded strial margin (inset shows cross section of rounded margin). 12) S. lahontanensis, pronotal marginal bead absent, sharply edged strial margin. 13) S. winnemucca, pronotal marginal bead absent, sharply edged strial margin. 14) S. wintoni, pronotal marginal bead absent, sharply edged strial margin, note striae also wider towards base (inset shows cross section of sharp edge). 15) S. wintoni, fused elytra removed exposing strap-like hind wings.

Figures 16–23. Stenotothorax protibiae dorsal (top) and ventral (bottom) surfaces. Note abrasions on ventral surfaces. 16, 20) S. ovipennis, lacking secondary dorsal row of setae. 17, 21) S. wintoni, with secondary dorsal row of setae proximal of basal tooth. 18, 22) S. comosus, with coarse setose punctures on ventral surface, female with sparse setae on medial margin. 19, 23) S. winnemucca, with coarse setose punctures on ventral surface, male with denser setae on medial margin. Arrow points to secondary row of setae.

Figures 42–47. Stenotothorax wintoni, n. sp. 42) Dorsal habitus. 43) Ventral habitus. 44) Lateral habitus. 45) Oblique anterior view head to elytral base. 46) Epipharynx. 47) Male genitalia, lateral view.