Stenotothorax odontomonteus 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 : 21-23

Stenotothorax odontomonteus Skelley and McPeak , new species

Figures 5 , 11 , 48–53

Diagnosis. Stenotothorax odontomonteus is distinguished from other members of the genus by the following combination of characters: protibia with secondary setal row, clypeus narrowed, small body size (most <6 mm length), clypeal margin bluntly angulate each side of emargination (not dentate) and lacking setal fringe, and pronotal basal groove and bead reduced. Stenotothorax odontomonteus appears to be restricted to the Cascade Mountain range east of Mt. Hood, Oregon. Other members of the nevadensis complex have distinctly, sharply dentate clypeal teeth.

Description. Holotype male length 5.3 mm, width 2.2 mm. Body shape elongate; color black, glossy. Head with clypeus narrow, distance between anterior most point of clypeal marginless than distance from teeth to frontoclypeal suture; clypeal anterior margin upturned and roundly angulate each side of emargination, setal fringe absent; clypeal surface granulate and finely punctate anteriorly; rest of head surface smooth and finely punctate; extreme base of vertex with few moderate punctures and weakly rugose (not visible with head retracted); frontal lobe projecting, angulate. Epipharynx with apical margin sinuate, tylus projecting; chaetopedia few and stout; epitorma broad ( Fig. 52 ). Pronotum transverse, widest anterior of middle, constricted in basal half, surface near anterior angles not explanate; disc punctation of two sizes, fine punctures as on head evenly distributed, coarse punctures roughly 5× larger than fine punctures evenly widely irregularly scattered; lateral margins lacking setal fringe, evenly arcuate from middle anteriorly and posteriorly to base, posterior angles weakly visible; basal margin weakly convex at middle otherwise nearly flat, with marginal groove and bead at middle fine, reduced to lacking on either side. Scutellum triangular, coarsely punctate basally, impunctate apically. Elytra fused, elongate; each humerus weak, humeral denticle present; striae distinct, strial sides weakly or not crenated, sides rounded; striae I–V reaching base, not wider toward base or over declivity; strial punctures fine; all interval punctation indistinct, fine, arranged in two vague rows, intervals weakly convex; epipleural fold setose only at extreme base. 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; ventral surface lacking groups of coarse punctures; protibial spur evenly curved inwardly; lacking ventral projections at medial apex beneath spur and along medial basal margin. Meso- and metafemur finely punctate on ventral surface, few coarse punctures less distinct than profemur. Meso- and metatibia gradually widening before abruptly dilated apex. Meso- and metatibial spurs narrowed, saber-like; lower mesotibial spur sexually dimorphic, 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 only 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, glossy 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. 53 ).

Sexual dimorphism. Female mesotibial lower spur unmodified. Male protibia have the inner apical margin slightly convex, with the marginal row of setae much denser and shorter apically than basally.

Variation. Length 4.48–6.3 mm, width 1.9–2.6 mm. Color of some specimens is dark red-brown, suspected to be younger or more teneral. Clypeal granulations may occupy the anterior half or cover nearly the entire clypeus up to the frontoclypeal suture. Lateral pronotal margin varies in the sharpness of the medial arcuate curve; a few are evenly curved from anterior angle to posterior angle, the majority are more strongly curved at middle, and one specimen has the middle curve nearly angulate. This last example gives the pronotal margin a distinct anterior and posterior region. Worn specimens have standard reduction of clypeal and protibial teeth.

Type material. Holotype: “/ OREGON: Wasco Co., Mt. Hood Nat. For. 4388 ft, ~ 18 mi. W of Dufur on NF-44; deer dung, frozen ground; 11-NOV-2015, 45°24.032′, −121°28.769′ / P. Skelley, K. Schnepp, R. McPeak, K. Arguez / [red paper] HOLOTYPE Stenotothorax odontomonteus Skelley&McPeak /”. Deposited in FSCA.

Allotype and paratypes (n = 163): OREGON: Hood River Co.: Parkdale, McCarthy Tree Farm , 45.52827°N, 121.57989°W, 22-X-2012, K. Larsen [1 RMPC] ; Wasco Co.: same data as holotype [allotype female and 12 FSCA] ; Mt. Hood N. F., W. of Pine Grove , 8 mi. E. Hwy-26 on Rt-216, milepost 8, 45°06.216′N, 121°27.802′W, 3356 ft, 11-XI-2015, P. Skelley, K. Schnepp, R.H. McPeak, K. Arguez [2 FSCA] ; same locality, 11-XI-2015, K.E. Schnepp [2 KESC] ; 2.1 mi. W Camp Baldwin on Hwy 44, 45°24.143′N, 121°27.587′W, 4111 ft, 5-IX-2013 to 14-V-2014, R.H. McPeak [3 FSCA, 7 RMPC] ; W. of Dufur on NF-44, 45°24.032′N, 121°28.769′W, 4388 ft, 12-XI-2015, R.H. McPeak [5 RMPC] ; ~ 10 mi. W. of Dufur on NF-44, 45°24.822′N, 121°19.529′W, 2706 ft, 11-XI-2015, P. Skelley, K. Schnepp, R.H. McPeak, K. Arguez [6 FSCA, 10 KESC] ; same locality, 22-XI-2015 to 24-II-2016, R.H. McPeak [1 RMPC] ; 8 mi. E of Hwy 26 on Hwy 216, 45°06.216′N, 121°27.802′W, 3356 ft, 11-XI-2015 to 1-IV-2016, R.H. McPeak [3 FSCA, 2 RMPC] ; 8 mi. E of Hwy 26 on Hwy 216, 45°06′14.82″N, 121°27′43.73″W, 3180 ft, 6-VII-2006 to 12-III-2007, R.H. McPeak [2 RMPC, 1 WBWC] ; same locality, 17-XI-2008 to 31-V-2009, R.H. McPeak [2 DCGC, 3 FSCA, 1- NMHL, 19 RMPC, 2 USNM] ; same locality, 4-XI-2009 to 10-IV-2010, R.H. McPeak, [7 FSCA, 14 MJPC, 39 RMPC, 3 UNSM, 5 WSU, 10 WBWC] .

Observed habits. Specimens collected in late fall and winter in barrier pitfall traps, in deer dung, and on freshly chewed deer bones. Some were found on deer dung under melting snow. These observations may indicate dispersing young adult feeding habits more than potential oviposition sites. Much fieldwork is needed to discover larvae and true habits for this and most other species of Stenotothorax .

Remarks. Members of the nevadensis complex are readily distinguished from other complexes by the dentate clypeus lacking a setal fringe, protibia with a secondary row of setae, pronotum with a reduced basal groove and bead, and moderate to small body size. Stenotothorax odontomonteus is probably the most easily recognized and geographically isolated member of the complex. Other members of the nevadensis complex have wider distributions and are more similar in morphology. These species need more character analysis before any conclusions can be drawn on their status.

Etymology. “Odontomonteus” is an intentional anagram of “Mount Hood Steno” with the letter “h” removed. Coincidentally, this anagram matches the combination of the classical roots “ odonto ” (Greek) and “ monte ” (Latin) with a Latinized suffix “-us”, which appropriately defines the species as the toothed one on the mountain.

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 48–53. Stenotothorax odontomonteus, n. sp. 48) Dorsal habitus. 49) Ventral habitus. 50) Lateral habitus. 51) Oblique anterior view head to elytral base. 52) Epipharynx. 53) Male genitalia, lateral view.