Stenotothorax lahontanensis 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 : 25-27

Stenotothorax lahontanensis Skelley and McPeak , new species

Figures 8 , 12 , 60–65

Diagnosis. Stenotothorax lahontanensis is distinguished from other members of the genus by the following combination of characters: protibia with secondary setal row, clypeus with four or more teeth and setal fringe, pronotal basal groove and bead reduced, coarse pronotal punctures smaller (only 2–3 times larger than fine punctures) and widely scattered, elytral striae wider and sharply edged at base, and elytra with short lateral fringe of setae. Stenotothorax lahontanensis appears to be restricted to an area of small dunes southeast of Pyramid Lake from Wadsworth to Fallon in Nevada.

Description. Holotype male length 5.8 mm, width 2.8 mm. Body somewhat hour-glass shaped, widest at apical third of elytra; color dark red-brown, glossy. Head with clypeus narrow, distance between anterior most point of clypeal marginless than distance from teeth to frontoclypeal suture; clypeus with anterior margin spiniformly dentate, with 2 primary teeth, 2 smaller teeth medially on the median emargination, one distinct smaller tooth lateral of the primary teeth followed by strong tooth-like crenulations toward the frontal lobes; clypeus fringed with short setae; anterior clypeal surface with few short indistinct setae; clypeal surface rugosely granulate on apical half, sculpture reducing in intensity towards the frontoclypeal suture, where it is weakly granulate; frontal punctation distinct, fine, 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. 64 ). Pronotum posteriorly hemispherical in shaped, widest anteriorly, constricted in basal half; surface near anterior angles not explanate; disc punctation of two sizes: fine punctures evenly distributed; coarse punctures evenly widely scattered, separated by 4 or more diameters, 2–3× larger than fine punctures; lateral margins 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, 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–VI attaining base, sharply edged and distinctly wider at base; interval punctation fine, arranged in two vague rows, surface weakly convex; epipleural fold with short; strial punctures fine; sparse, setae along ventral surface in addition to base. 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; 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; of similar shape, elongate. Meso- and metatibia gradually widening before abruptly dilated apex. Meso- and metatibial spurs narrowed, saber-like; lower mesotibial spur respectively 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 glabrous medially. Male genitalia with parameres shorter than basal piece; sharply angled ventrally at apical third to bluntly pointed apex in lateral view ( Fig. 65 ).

Sexual dimorphism. Female lower mesotibial spur similar to male. Male protibia have the inner apical margin slightly convex, with the marginal row of setae slightly denser and shorter apically than basally. Setae may be worn or matted.

Variation. Length 5.8–6.3 mm, width 2.7–2.9 mm. Older specimens show typical signs of wear on protibial and clypeal teeth. Setae on the anterior clypeal surface are present, but often worn away on older specimens. Secondary clypeal teeth vary in number and size, in part due to wear.

Type material. Holotype: “/ NEVADA: Churchill Co., jct. Hwys 50 & Alt. 50, W. of Fallon , elev. 4030′, XI-20-2008, P.E. Skelley, F. Skillman, W.B.Warner / 39°30′43″N, 118°56′36″W, sand/organic matter under plant on “dunes” / [red paper] HOLOTYPE Stenotothorax lahontanensis Skelley&McPeak /”. Deposited in the FSCA.

Allotype and paratypes (n = 210): NEVADA: Churchill Co.: same data as holotype [43 FSCA, 68 WBWC, 2 WFBM] ; 3.2 mi. WSW. jct. Hwys 50 & alt. 50, W of Fallon, 39°28′48″N, 118°58′54″W, 4070 ft, 20-XI-2008, Skelley, Skillman, Warner [allotype and 10 FSCA, 14 WBWC] ; same locality, 15-20-XI- 2008, Skelley, Skillman, Warner [3 RMPC] ; Washoe Co.: dunes 3 km SW of Wadsworth , 39°36′59″N, 119°18′19″W, 17-XI-2008, W.E. Steiner, et al. [4 CMNC, 2 CNCI, 4 DCGC, 45 FSCA, 4 NHML, 4 USNM] ; nr. Wadsworth off I-80, 17-XI-2008, A.D. Smith [5 MJPC] .

Gordon and Skelley (2007) report data for S. parapyriformis (Gordon and Skelley) from Nevada: Churchill Co., Stillwater NWR, Pintail Bay, 23 Feb., 15 Mar., 1998, R.W. Rust and M. Rahn. Specimens from this locality were not available for confirmation. However, they are expected to be S. lahontanensis .

Observed habits. The majority of the type series were sifted from under plants in small dunes in November.

Remarks. Stenotothorax lahontanensis is most similar to S. parapyriformis which has larger coarse pronotal punctures, elytral striae VI not attaining base, and is found at the eastern side of the Great Basin in southwestern Utah. Both species are similar to the intervening populations of S. pyriformis , which has distinct long fringe of elytral epipleural setae, and coarse pronotal punctures more numerous and densely distributed.

Etymology. Specific epithet is from the Pleistocene Lake Lahontan, which dried to become a series of smaller lakes, around which we hypothesize the pyriformis complex speciated. Stenotothorax lahontanensis is from one of the dry beds near the present-day Lahontan Reservoir.

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 60–65. Stenotothorax lahontanensis, n. sp. 60) Dorsal habitus. 61) Ventral habitus. 62) Lateral habitus. 63) Oblique anterior view head to elytral base. 64) Epipharynx. 65) Male genitalia, lateral view.