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Darkling Beetle - Coelocnemis magna

Darkling Beetle - Coelocnemis magna
Pottery Canyon, La Jolla, Orange County, California, USA
June 28, 2003
approx. 3 cm

Moved from Coelocnemis.

Moved from Coelocnemis.

Darkling beetle, Coelocnemis
Don't sweat it, I got them confused alot before I figured out some subtle differences. This is a species of Coelocnemis, same family (Tenebrionidae).

I've moved it -- but what are the differences? Are they in Borror? I think we probably have Eleodes around here as well, at least that's what we called them when I took Field Ent. back in the '70s.

Coelocnemis vs. Eleodes
Sounds like a sci-fi movie:-) Well, I usually recognize Coelocnemis by its more oval appearance, and the pronotum (thorax) is just huge compared to Eleodes. You have to see the two side-by-side. Also, Eleodes often has the elytra (wing covers) striated (grooved), or granular in texture, whereas many of the common Coelocnemis are smooth.

which one smells worse?
I was actually wondering about the pronotum. There are a lot of these things misidentified out there on the web!

this is C. magna
Mimics Eleodes grandicollis and/or acuticaudus depending on exactly where it is. And they both smell bad, although Coelocnemis seems less trigger happy. An interesting project would be to determine just how similar the defensive secretions are.

Just wondering...
What benefits does this species have to gain by mimicking Eleodes? Both Eleodes and Coelocnemis have defensive secretions, so I don't see a good reason why these would decide to mimic Eleodes.

One of biology's great mysteries. Mullerian mimicry - the theory is that two noxious organisms mimic one another and gain added protection from predators that way.

Probably why most large beetles in the desert are black.

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