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Entomology (Study of Bugs)/Identification of Beetle


QUESTION: I took a picture of a beetle near Arches National Park in Utah
on July 4 mid-morning.  It walked in the sand.  It was an unusual
beetle in that it had a projection at the end of its' abdomen.
Could it be a Darkling Stink Beetle?  I've attached a picture of


Yes, it is a type of darkling beetle, probably Eleodes caudiferus :

Please consider submitting your own image to Bugguide, as there are not many images there right now.

Neat find!


---------- FOLLOW-UP ----------

QUESTION: Do you have information on Eleodes caudiferus if it uses chemical defense against predators meaning that is what the tail is for.
The text mentions that it's found in Texas and Arizona.  We were
at Toroweap in Arizona and I might have been mistaken on the


Well, there is at least one other species of Eleodes found in Arizona that sports those "tails," but the one I cited is the more common species....

The "tails" are simply extensions of the elytra (wing covers), which are fused in Eleodes , a flightless beetle.  As far as I know, all Eleodes secrete hydroquinones in defense.  These are volatile, strong-smelling chemical compounds secreted from glands near the anus.  It may be that the "tails" spread the aromatic compounds over a larger area (since the compounds are liquid when initially secreted and then become gaseous).  Never thought about that possibility before....

Hope that helps.


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Eric R. Eaton


I answer insect and spider identification questions ONLY. Attach images if possible. No "what bit me?", "what do I feed this bug in captivity?", or science fair project questions please. NO TECHNICAL QUESTIONS ABOUT INSECT PHYSIOLOGY.


Principal author, Kaufman Field Guide to Insects of North America. Professional entomologist employed previously at University of Massachusetts, Chase Studio, Inc., and Cincinnati Zoo; contract work for West Virginia Department of Natural Resources, Smithsonian Institution, and Portland (Oregon) State University.

Author, Kaufman Field Guide to Insects of North America, Missouri Conservationist magazine, Ranger Rick, Birds & Blooms, Timeline (journal of the Ohio Historical Society). I have contributed to several books as well.

Oregon State University, undergraduate major in entomology, did not receive degree.

Awards and Honors
One of the top 50 experts in all categories for, 2009.

Past/Present Clients
Principal author of the Kaufman Field Guide to Insects of North America, Smithsonian Institution (contract), Cincinnati Zoo (employer), Portland State University (contract), Chase Studio, Inc (employer), Arkansas Museum of Discovery (guest speaker). Currently seeking speaking engagements, leadership roles at nature festivals, workshops, and ecotours.

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