Key to North American Elonus Species

1. Elytra uniformly dark brown with pattern of white setae consisting of a median wavy transverse stripe, two basal patches, and an apical band (Figure 1i)........................................................ E. nebulosus (LeConte, 1875)

- Elytra bicolored: base entirely orange or with an orange blotch on each elytron, rest of the elytra brown to black (Figure 1a–h).................................................................................................... 2

2. Short elytral pubescence between punctures dense, white, uniform, distinctly visible under lateral illumination (Figure 4e–f) 3

- Short elytral pubescence between punctures sparser, darker, hardly visible, or limited to suture and a post-median stripe (Figure 4g –j)............................................................................................ 4

3. Elytra brown (except base), uniformly covered with long erected yellow setae (Figure 4f). forelegs and midlegs reddish. Male mesotibiae strongly curved (Figure 3l)................................................. E. hesperus Werner, 1990

- Elytra black, long pale pubescence darker, only with white setae along suture (Figure 4e). Male mesotibiae with moderate curvature (Figure 3n)............................................................... E. chisosensis Werner, 1992

4. Base of elytra marked with a solid, uninterrupted transverse orange stripe, only moderately narrower in scutellar region (Figure 4c)................................................................................................. 5

- Base of elytra marked with orange patches confined to humeral callus on each side; or orange markings forming a continuous stripe but with a strong constriction in the scutellar region (Figure 4a, b).............................. E. gruberi n. sp.

5. Elytra with a post-median band of whitish pubescence, distinct under side illumination, composed of short recumbent setae interspersed between elytral punctation (Figure 4h, arrows). Male genitalia much longer than in other species (Figure 2a)................................................................................... E. basalis (LeConte, 1855)

- Elytra without pattern of whitish pubescence................................................................ 6

6. Thorax and head half the width of elytra at their base; male mesotibiae with a kink (Figure 3m)... E. excavatus Werner, 1992

- Thorax and head at least 60% of elytra width at their base; male mesotibiae evenly curved......... E. simplex Werner, 1992