Entomoderes satanicus | Ruta Nacional 20 @ km 367, San Luis Province, Argentina

This past February while traveling to see research plots in Argentina, I had the pleasure of accompanying colleague and scarab expert Federico Ocampo to San Juan Province in west-central Argentina to see some of the endemic scarabs that live in the sand dunes that dot the region. Along the way we made a quick stop at a sandy spot along Ruta Nacional 20 in San Luis Province to see what was out and about. Several interesting insects were seen, but one of the most impressive was this marvelously armoured darkling beetle (family Tenebrionidae) belonging to the genus Entomoderes—also endemic with nine species ranging from southern Bolivia to central Argentina (Flores & Roig-Juñent 1997).

Stout spines and a heavily sclerotized body surely provide effective anti-predation defense…

The stout, backwards-directed lateral spines on the pronotum are as evil as any I’ve ever seen, perhaps being the the reason behind the most awesome species epithet I have ever encountered—satanicus! Actually, there was some question about whether it represented this species or another in the genus with an almost equally awesome name—draco! I wasn’t able to access the more recent, paywall-protected revision by Flores & Roig-Juñent (1997); however, a relatively recent prior work (Peña 1990) seems to confirm its identity as the former by the presence of distinct raised costae on each elytron between the lateral keel and sutural margin confirm.

…but not from tiny enemies (note parasitic mite on the venter behind the right procoxa).

Surely the sharp, stout spines and heavily sclerotized, ridged body provide effective protection from vertebrate predators and perhaps also help to minimize loss of water, since all of the species are found strictly in arid habitats (Peña 1990). I did not collect the specimen, but many such heavily sclerotized darkling beetles can be difficult to nearly impossible to pin by normal means (I have actually used a hammer to help in the case of one species I collected in South Africa. Seriously!), and I’m sure this one would have been no different. For all its armoured protection, however, there still remain chinks—note the tiny, bright red, parasitic mite on the ventor behind the right procoxa in the last photo.

REFERENCE:

Flores, G. E. & S. Roig-Juñent. 1997. Systematic revision of the Neotropical genus Entomoderes Solier (Coleoptera: Tenebrionidae). Insect Systematics & Evolution 28(2):141–162 [abstract].

Peña, L. E. 1990. El género Entomoderes Solier (Coleoptera: Tenebrionidae). Boletin del Museo Nacional de Historia Natural Textos sobre patrimonio natural de Chile 37:253–259 [ISSUU].

© Ted C. MacRae 2015