Philolithus elatus, formerly known as Gonasida elata, is widespread throughout western North America. It is considered to be a Batesian mimic of Eleodes obscura. Although it is readily found around the lab in late summer and early fall, it appears to be uncommon in most of its range, which may explain the relatively sparse literature on the species.

Identification (Brown, 1971; Smith, 2013):

Size: 21-35 mm

Subfamily: Pimeliinae

Tribe: Asidini

Subgenus:Gonasida

Description (Quoted directly from Brown, 1971): Body elongate-suboval, constricted at the waist, convex, and virtually glabrous. Pronotum distinctly margined laterally, widest before middle; the margin varying from dilated, aliform and strongly reflexed, to moderately convex and deplanate. Pronotum disk smooth, weakly convex, minutely punctate medially; the punctae becoming larger laterally in the concavity at the origin of the reflexure. Lateral margin crenulate, studded with a few small, stiff setae; rugose dorsally and ventrally. Base of pronotum truncate. Side of pronotum beneath margin smooth and sparsely, sometimes deeply, punctate, becoming rugose near coxa. Mesepimeron with slightly larger punctae, prosternum coarsely punctate, mesosternum rugose. metasternum smoother and lightly punctate. Scutellum convex, equilatero-triangular to elongate triangular. Elytra elongate-fusiform, almost twice as long as wide; convex, widest behind middle; humeri prominent and averted. Width of elytra at humeri equal to width of pronotum at base. Surface sculpture varying from smooth to tortuously rugose, or deeply sulcate. Lateral margin absent to sharply creased and carinate. Epipleural fold convex, and visible over entire length, abdomen smooth, weakly punctulate. Length, 21 to 35 mm.

Remarks (my additions indicated by brackets): This species is one of the most distinctive tenebrionids in western North America. Among the other Asidini, only the Stenomorpha marginata group, and members of the genus Megasida approach it in size. In overall habitus, it most resembles the unrelated tenebrionid Eleodes obscura, which it seems to mimic. Only Tisamenes truguii Champion, of central Mexico, probably its closest relative, shows a similar development of the pronotum. The following key should be of assistance in separating the four subspecies of Gonasida elata [Philolithus elatus]. However it should be pointed out that it took a statistical key to achieve 90% separation of the subspecies. Used alone, this conventional dichotomous key would probably not give equivalent results , but used in conjunction with the distribution map [presented below], quite reliable determinations should be possible .

Key to the subspecies of Gonasida elata [Philolithus elatus] (Leconte)

1. Carinae of elytral disk flat, or weakly convex; often not evident or obliterated by rugosities ; intervals between carinae always flat•••• • ••••••• ••••••••• •• ••••••••••••• 2

1′. Carinae of elytral disk convex , and evident; never rugose; intervals between carinae at least moderately convex••• 3

2(1). Lateral margin of pronotum strongly averted, sharply angled, and steeply reflexed•••••••••••••••• subspecies elata

2′. Lateral margin of pronotum weakly to moderately averted, blunt, and not or weakly reflexed •••••••• subspecies inferna

3(1′). Lateral margin of pronotum strongly everted, sharply angled, and steeply reflexed• ••••••••••••••• subspecies difformis

3′. Lateral margin of pronotum moderately averted and bluntly angled , to not ever ted and evenly convex; not or weakly reflexed••••••• •••••·•••••••••••subspecies compar

Range

Philolithus elatus is found thoughout the high plains of western North America. The four subspecies occupy different portions of the species’ range, although P. e. compar is more widespread than the others. Map based on Brown et al., 1971.

References

Brown, K. W. (1971). A population approach to computer taxonomy with applications in the genus Gonasida.

McIntyre, N. E. (1999). Use of Pogonomyrmex nest-sites by Tenebrionid beetles (Coleoptera: Tenebrionidae) for oviposition and thermoregulation in a temperate grassland. The Southwestern Naturalist 44, 379–382.

Slobodchikoff, C. N. (1978). Experimental Studies of Tenebrionid Beetle Predation By Skunks. Behav 66, 313–322.

Slobodchikoff, C. N. (1983). Water Balance and Temperature Preferences, and Their Role in Regulating Activity Times of Tenebrionid Beetles. Oikos 40, 113.

Smith, A. D. (2013). Phylogenetic revision of the North American Asidini (Coleoptera: Tenebrionidae). Systematic Entomology 38, 585–614.

Smith, A. D., Wilson, J. S. and Cognato, A. I. (2015). The evolution of Batesian mimicry within the North American Asidini (Coleoptera: Tenebrionidae). Cladistics 31, 441–454.

Stapp, P. (1997). Microhabitat Use and Community Structure of Darkling Beetles (Coleoptera: Tenebrionidae) in Shortgrass Prairie: Effects of Season Shrub and Soil Type. American Midland Naturalist 137, 298.

Wise, D. H. (1981). Seasonal and Yearly Patterns in the Densities of Darkling Beetles (Coleoptera: Tenebrionidae) in a Montane Community. Environmental Entomology 10, 350–358.