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Eusattus reticulatus? - Eusattus convexus

Eusattus reticulatus? - Eusattus convexus
Las Cruces, Doña Ana County, New Mexico, USA
December 28, 2005
Size: 12 mm
Found four of these on warm, sunny afternoon. Two were caught in spider webs along rock wall. One of those was dead. The two remaining beetles were scurrying about in bright sunlight. These are the largest beetles I've found so far on my visit to New Mexico. I don't recognize the family. They have some impressive straight tibial spurs that might help identify them. They produced no aroma that might help ID them.

Images of this individual: tag all
Eusattus reticulatus? - Eusattus convexus Eusattus reticulatus? - Eusattus convexus Eusattus reticulatus? - Eusattus convexus Eusattus reticulatus? - Eusattus convexus Eusattus reticulatus? - Eusattus convexus Eusattus reticulatus? - Eusattus convexus

Drumming beetle
Don Chandler told me in private correspondence that he thought he recalled his advisor at Ohio State, Chuck Triplehorn, "was interested in Eusattus muricatus because they will 'drum' by tapping the tips of their abdomens to the ground, for what reason I can't recall. If you put them in a tin plate you can hear it quite clearly."

I planned to test these beetles until it was determined they were a different species. However, in a photo session today, my subject clearly drummed on three occasions, lasting a little less than a second and consisting of an estimated 10 to 20 beats each time. The beetle seemed to do this out of annoyance or frustration at failing to crawl under a stainless steel ruler in my light arena.

The tip of the abdomen appeared to be the percussion instrument, and the drumming was rather amplified by the hollow beneath the piece of colored foam-core I used for a background.

My conjecture here is that, at least two Eusattus species are drummers and that possibly the entire genus exhibits this behavior. An interesting finding would be whether there are quantitative differences between the species' drumming (beats per second, total beats per drumming, etc.) Also, would they drum if attacked by ants, and with what effect? Do both sexes drum? How do nearby members of the same species react when one beetle drums?

Eusattus convexus
Don Chandler, in private correspondence, says collection specimens of this species from the nearby White Sands National Monument look most like these images, although E. muricatus bears close resemblance.

Yep, its STILL a tenebrionid:-) That is one diverse family.

Eusattus muricatus??
I am pretty sure this is a Eusattus, and E. muricatus is a likely pick. However, it has been so long since I have identified tenebs that the genus could have changed by now.

Not confirmed.
Solitary image of E. muricatus online does not match, so my guess is it's another species in same genus. Five species are listed by New Mexico Game & Fish Dept.: Eusattus convexus, difficilis, muricatus, puberulus, and reticulatus. Reticulatus is the only one on their site listing Doña Ana County in its range, but the others are not necessarily excluded.

If anyone has access to Systematics of Eusattus and Conisattus (Coleoptera, Tenebrionidae, Coniontini, Eusatti) by John T. Doyen, I'll bet this one's ID could be found easily. The copy nearest me is in the Dartmouth College Library -- a bit of a hike for me.

Thanks Eric
I'll stick them on the family page after a bit.

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