Stenotothorax smilodon 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 : 13-15

Stenotothorax smilodon Skelley and McPeak , new species

Figures 36–41

Diagnosis. Stenotothorax smilodon is distinguished from other members of the genus by the following combination of characters: protibia with secondary setal row, broad head, clypeus with two nearly spiniform teeth, pronotum explanate at anterior angles, pronotal basal groove and bead distinct across width. Stenotothorax smilodon appears to be restricted to the western Snake River Plain in eastern Oregon and southwestern Idaho.

Description. Holotype male length 6.9 mm, width 3.3 mm. Body elongate; color dark red-brown nearly black, glossy, weakly dull. Head with clypeus broad, distance between anterior most point of clypeal margin roughly equal to distance from angle (teeth) to frontoclypeal suture; clypeus anterior margin with a nearly spiniform tooth either side of median emargination, margin with setal fringe short to absent, indistinct in dorsal view; clypeal surface rugose and densely, finely punctate nearly up to frontoclypeal suture; surface from base of clypeus to vertex with strong, fine, dense punctures; frontal lobe projecting, angulate. Epipharynx with apical margin sinuate, tylus projecting; chaetopedia few and stout, numerous and fine; epitorma broad ( Fig. 40 ). Pronotum transversely subrectangular, widest at middle, narrowing in basal half, explanate near anterior angles; punctation on disc of two sizes, fine punctures evenly distributed, coarse punctures roughly 10–12× larger than fine punctures; lateral margins lacking setal fringe, evenly arcuate anteriorly, more strongly so posteriorly, posterior angle indistinct; basal pronotal groove broad and bead distinct across width, slightly reduced either side of middle, continuous with lateral groove and bead. Scutellum triangular, coarsely punctate basally, impunctate apically. Elytra fused, elongate; each humerus rounded, humeral denticle distinct in dorsal view; striae distinct, fine, edges rounded; striae I–IV deeper and wider near base and on declivity; strial punctures fine, weakly crenating sides; intervals all similarly developed, weakly convex, moderately glossy; interval punctation fine, scattered, arranged in vague rows on more lateral intervals; 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; protibia lacking ventral projections at medial apex beneath spur and along medial basal margin; protibial spur evenly curved inwardly. 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, stout, 1/3–1/2 length of upper spur, bent inward at apex. Meso- and metatarsomere I length = length of 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 and apical sternites punctate as basal sternite laterally, glossy and impunctate medially. Male genitalia with parameres shorter than basal piece; sharply angled ventrally at apical third to bluntly pointed apex in lateral view ( Fig. 41 ).

Sexual dimorphism. Female lower mesotibial spur unmodified, 1/2 length of upper spur. Male protibia narrower than in female.

Variation. Length 6.5–8.1 mm, width 3.0– 4.1 mm. Worn specimens show varying degrees of reduction in clypeal teeth. A couple specimens lack these teeth and have notably worn protibial teeth.

Type material. Holotype male: “/ 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 / N43°54′24″ W116°48′59″, mouths of rodent burrows excavated by badgers / [red paper] HOLOTYPE Stenotothorax smilodon Skelley&McPeak /”. Deposited in the FSCA.

Allotype and Paratypes (n = 34): IDAHO: Payette Co.: same data as holotype [allotype female and 1 FSCA, 1 USNM] ; Washington Co.: Andrus WMA, 44.7623°N, 116.8479°W, 1538 m, 15-XI-2012, R. Winton [3 RMPC] .

OREGON: Baker Co.: Exit 338 on I-84, jct. Lookout Mt. Rd. , 44°28′27″N, 117°20′22″W, 2360 ft, 12-21-XI-2014, Skelley , Schnepp , Powell [4 FSCA] ; Exit 338 on I-84, jct. Lookout Mt. Rd., 44°28′27.51″N, 117°20′19.75″W, 2360 ft, 12-XI-2014, K.E. Schnepp [1 KESC] ; Exit 338 on I-84, jct. Lookout Mt. Rd., 44°28.448N, 117°20.327′W, 2332 ft, 30-IX-2014 to 22-II-2015, R.H. McPeak [2 FSCA, 1 RMPC] ; same locality, 22-II-2015 to 13-IV-2015, R.H. McPeak [1 FSCA, 2 RMPC] ; Hwy 84 & Lookout Mtn. Rd., 44°28.445′N, 117°20.361′W, 2359 ft, 9-X-2013 to 17-IV-2014, R.H. McPeak [2 FSCA, 3 RMPC] ; Lookout Mtn. , near corral, 44°32.399′N, 117°16.845′W, 5218 ft, 30-IX-2014 to 22-II-2015, R.H. McPeak [1 FSCA] ; Malheur Co.: Moors 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, 4 RMPC] ; Lytle Blvd , 9.5 km S. Vale, T19S R45E S24, 2680 ft, 25-IX-1983 to 12-XI-1983, William H. Clark, Mary H. Clark [1 OJSM] .

Observed habits. Some of the specimens were collected in burrows of a species of Thomomys Wied- Neuwied ( Rodentia : Geomyidae ), others were collected from rodent burrows excavated by badgers. These latter burrows also had S. schneppi Skelley and McPeak , n. sp., at their entrance. As with other large species of Stenotothorax , available data indicates they may have an association with burrowing rodents. More field observations are needed to substantiate this hypothesis. They have been collected in barrier pitfall traps and walking on snow. Ross Winton (in litt.) states, “The ones I collected were out by the hundreds probably around 5pm but the cloud cover and snowfall were so dense it felt more like dusk. I found it easiest to collect on closed roads with no tracks in the middle of intact habitat (in this case sagebrush steppe). This allowed for better visibility of the beetles against the white background.”

Remarks. Stenotothorax smilodon is most similar to S. mcpeaki , most notably differing in that S. mcpeaki lacks clypeal teeth and has an isolated distribution along the Columbia River of Oregon and Washington. If an explanate pronotum and clypeal teeth are considered to be easily derived characters, then these two species along with S. niviviator share many body and genitalic characteristics, indicating they may form a species complex.

Etymology. This is the largest species of Stenotothorax with distinct clypeal teeth, which we had nicknamed “big and toothed”. It seems fitting to name it after another big and toothed animal, the saber-toothed cat, Smilodon Lund ( Carnivora : Felidae ), which also occurred in western North America. Although there are no morphological similarities between the two, we like the name, which is being applied as a noun in apposition.

Figures

Figures 36–41. Stenotothorax smilodon, n. sp. 36) Dorsal habitus. 37) Ventral habitus. 38) Lateral habitus. 38) Oblique anterior view head to elytral base. 40) Epipharynx. 41) Male genitalia, lateral view.