Stenotothorax niviviator 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 : 11-13

Stenotothorax niviviator Skelley and McPeak , new species

Figures 4 , 10 , 30–35

Diagnosis. Stenotothorax niviviator is distinguished from other members of the genus by the following combination of characters: protibia with secondary setal row, pronotum broad but not laterally explanate, pronotal basal line and bead distinct across width, pronotal lateral marginal bead weakly thickened anteriorly, elytral humerus rounded to weakly angulate not dentate, and dorsally with fine distinct punctation dense enough to make surface appear dull. Stenotothorax niviviator appears to be restricted to mountainous areas of west central Idaho.

Description. Holotype male length 7.8 mm, width 3.4 mm. Body elongate, color dark red-brown, dull. Head with clypeus broad, distance between anterior most point of clypeal margin equal to distance from apex to frontoclypeal suture; clypeus with anterior margin distinctly emarginated at middle, rounded on either side, setal fringe absent; surface moderately rugose or weakly granulate anteriorly, becoming smooth along frontoclypeal suture; entire surface from clypeus to vertex with distinct evenly distributed fine punctures; vertex with few widely scattered coarse punctures each side of middle; frontal lobe projecting, weakly angulate. Epipharynx with apical margin; nearly straight, gently concave entire length, tylus not projecting; chaetopedia numerous and fine; epitorma narrowed ( Fig. 34 ). Pronotum broad, transversely rectangular in dorsal view, widest at middle, dull; with distinct evenly distributed fine punctures; coarse punctures widely scattered, diameter = width of basal marginal groove, about 10 x larger than fine punctures, not denser laterally, lacking along anterior medial surface; anterior margins weakly explanate; lateral margins evenly arcuate anteriorly, becoming broadly rounded posteriorly, posterior angle indistinct, marginal bead weakly thickened anteriorly, lacking setal fringe; basal groove broad and bead distinct, not reduced, present on either side of middle when viewed dorsally, continuous with lateral groove and bead. Scutellum triangular, coarsely punctate basally, lacking punctures apically. Elytra fused, elongate; each humerus rounded, denticle weak and obtuse, sides evenly arcuate to parabolically rounded apex; striae all similar, distinct but fine, not more distinct or wider basally, slightly wider and deeper over declivity; striae I–VI reaching base, sides smoothly rounded; strial punctures fine and indistinct, strial sides not crenated; interval punctation distinct, fine, not arranged in rows, surface dull, weakly convex, all intervals similarly developed; epipleural fold setose at extreme 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; protibial lateral teeth with basal most tooth situated just anterior of mid-tibial length; protibial spur evenly curved inwardly; protibia lacking ventral projections at medial apex beneath spur and ventrally along basal median 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 narrow, blunt, apically inwardly hooded, 1/3–1/2 length of upper mesotibial spur. Meso- and metatarsomere I length = length of corresponding upper spur. Venter with metasternum short; densely coarsely punctate laterally, sparsely finely punctate medially. Abdomen with basal sternite coarsely punctate, setose and rugose across surface; medial sternites punctate as basal sternite laterally, glossy and impunctate medially; apical sternites entirely impunctate and glossy. Male genitalia with parameres shorter than basal piece; curved ventrally at apical third to acutely pointed apex in lateral view ( Fig. 35 ).

Sexual dimorphism. Female lower mesotibial spur unmodified, 1/2 length of upper spur.

Variation. Length 6.4–8.85 mm, width 2.9–3.8 mm. As with all species, some specimens show a large amount of wear on the tibia and clypeal margin. Other notable variation is in the number of coarse pronotal punctures, one specimen having roughly half as many as the most punctate specimen. Laterally the pronotal margin can be evenly arcuate to weakly angulate medially. The pronotal marginal bead is weakly thickened anteriorly in most specimens. In some, the marginal bead does not appear thickened anteriorly.

Type material. Holotype male: “/ 7 mi. N. Deary, IDAHO, Latah Co., XII-29-1966 / D. A. Barstow Collector / L. S. Hawkins, Jr. Collector / Stenotothorax lanei (Saylor) det. P. E. Skelley 2007 / HOLOTYPE Stenotothorax niviviator Skelley&McPeak /”. Property WFBM, deposited in FSCA.

Allotype and paratypes (n = 28): IDAHO: Benewah Co.: Crystal Cr. , 22-XII-1963, [2 WFBM] ; [labeled as Lanah Co.] Flat Creek , 15-XI-1952, W.F. Barr [1 USNM] ; Clearwater Co.: 5 mi. E. Bovill on Roger’s Cr. Rd. , 22-I-2005, P. Barrett, F. & J. Merickel [1 RMPC, 3 WFBM] ; Bovill , 21-I-2005, S.S. Gesdorf [1 WBWC] ; Musselshell R. S., 6-XII-1965, E.J. Allen [1 WFBM] ; Idaho Co.: Mud Creek Jct., 25-XI-1978, R.C. Biggam [1 RMPC, 3 WFBM] ; Lanah Co.: 3 mi. E. Robinson L., 8-I-1967, W.F. Barr [1 WFBM] ; 3.5 mi. E. Bovill , 11-XII-1978, R.C. Biggam [4 WFBM] ; 5.5 mi. E. Bovill , 11-XII-1978, R.C. Biggam [4 WFBM, 1 RMPC] ; same data as holotype [allotype female and 1 FSCA] ; Robinson L., 22-III-1978, W.M. Hanks [1 WFBM] ; Strychnine Cr. , 2 mi. N Laird Park, 12-XII-1954, K.D. Hallett [1 WFBM] ; 5 mi. N. Moscow, 11-XII-1968, P. Schroeder [1 RMPC] .

Observed habits. All specimens appear to have been hand collected, walking on snow in early winter.

Remarks. Stenotothorax niviviator is a cryptic species that will key to S. lanei in Gordon and Skelley (2007) . Stenotothorax lanei differs most notably in having a distinctly anteriorly thickened lateral pronotal marginal bead, distinct strial punctures, fine dorsal punctation, dorsal surface glossy, and male genitalia having parameres more elongate and only weakly curved. Other body and genitalic characters indicate a closer relationship with S. mcpeaki and S. smilodon , which differ in having a more explanate pronotal surface near the anterior angle. More analysis is needed to sort out these relationships.

Etymology. Whether a behavior or coincidence, many Stenotothorax species become active at the beginning of winter and are occasionally found walking on snow or in near freezing weather at night. Nearly all specimens of this species were collected “on snow”, thus, the species name “snow traveler” is appropriate. The epithet is a combination of the Latin “ nivis” meaning of snow and “ viator” meaning traveler or pilgrim.

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 30–35. Stenotothorax niviviator, n. sp. 30) Dorsal habitus. 31) Ventral habitus. 32) Lateral habitus. 33) Oblique anterior view head to elytral base. 34) Epipharynx. 35) Male genitalia, lateral view.