There are 129 species in the beetle genus, Eleodes. These large black beetles are found in dry desert conditions. Eleodes species secrete bad smelling liquids (stink) that deter ants and other predators of the desert. The bad odor is due to quinones that are synthesized by the beetle in glands located in the abdomen. If handled, they may spray quinones to advertise their bad taste. Entomologist and “Father of Chemical Ecology” Tom Eisner (who died earlier this year at 81) was keenly interested in Eleodes species and their defensive secretions. He wrote numerous articles about Eleodes beetles and featured them in his book and movie, Secret Weapons.
Eleodes beetles are sometimes called clown beetles or tumbler beetles because they will stand on the heads when disturbed. Since the defensive secretions come from the abdomen and the head is more vulnerable, the head down, butt up position maximizes their defense against large predators.
The Eleodes beetles are large but most are not pests. Many species feed on seeds, plants or are scavengers. The desert can be hot during the day and cold at night. The beetles are known to shelter in the burrows of kangaroo rats and other rodents. This one was rather sluggish in the cool morning air. I found the beetle sunning itself on a tree trunk outside my tent in South Eastern Nevada at Cathedral Gorge.
So how do I repel them? I don’t care what they do outside, but they’re a stinky pest when they invade indoors (and climb into bed with me — no, I’m not kidding!) Best thing I’ve found so far is WD-40, but it doesn’t completely work; some go right past it. I’m wondering if that new snake repellent might work (cedar oil, cinnamon, what amounts to laundry detergent, and I forget what else — cinnamon alone does not work). I’d try borax but I can’t get it in any decent quantity. 😦
They’re so thick this year, the incidence at night is about one beetle every 6 inches, plus clumps converged on anything organic. (And now that it’s dry season, they and the starving grasshopper plague are eating each other. Seriously, they are!)
I wish for a bunch of gopher snakes, that would help a lot!
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Quite by accident, I found a way to control excessive hordes of desert stink beetles:
Imidacloprid fly bait (made by Bayer). Flies ignore these sugar-based pellets, and so does everything else… but the black beetles are strongly attracted, suck it right down, and it kills them almost immediately. Makes it real easy to control both where they are (put bait out of reach and they’ll still congregate around it), how many are underfoot, and where the dead ones wind up.
Another story about how efficient they are as scavengers (or why the desert generally lacks all manner of organic debris): One day I killed a big rattlesnake (another thing we get in plague numbers). Laid it aside to ‘set up’ so it would be easier to skin. Came back four hours later and all that was left of this 4.5 foot long snake, big around as my wrist, was about 18 inches of the spine. The black beetles had eaten all the rest of it, and were still working hard on the remaining scraps.
PS. when you have a lot of gopher snakes, you have neither black beetles nor rattlesnakes — nor starlings!