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root borer beetle - Prionus californicus

root borer beetle - Prionus californicus
boise, Idaho, USA
July 12, 2007
Size: 2--2.5"
I found him in the bark by my house just sitting there, at about 11 at night, under my porch light. he made a weird squeaky sound when I picked him up onto the stick. he also had big jaws!!! I found something like him in a bug guide that's called a giant root borer, but i dont know for sure if that's him or not

Images of this individual: tag all
root borer beetle - Prionus californicus root borer beetle - Prionus californicus

Moved from Longhorned Beetles.

Prionus californicus.
This is a male of Prionus californicus most likely. Certainly genus Prionus at any rate. By rocking its head up and down, it rubs ridges against the inside margin of the thorax to create the squeaking sound, a form of sound production among many insects called "stridulation." Do be wary of those jaws. After all, it had to chew its way out of a tree to get here in the first place:-) Prionids are usually never abundant enough to cause serious damage, and/or tend to attack trees already weakened and dying from other causes anyway. The adults are attracted to lights at night, as you observed, but they don't live very long. Further, other animals like to eat them, including skunks, probably owls, and some bats.

Need help Identifying beetle.
Ok. First I have to say sorry for such a poor description. I was unable and unwilling to capture beetle. I seen this beetle that looks a little like the one here except...the beetle I saw was a darker grey/black color. It was 4 to 4 1/2 inches long and about 2 to 2 1/4 inches wide and flew onto my shirt in the middle of the night when I was out camping in the mountains of California a few days back. It had short stout antennas right on the end of its face sticking straight out left and right of his body about 3 to 3 1/2 inches.

I have been trying to search for the beetle online but have been unsuccessful in finding the same one that I saw. Prior to this site and the picture you have here I thought the Asian Longhorned Beetle was the closest I was going to find but as my description notes the antennas on the one that I saw are alot shorter and stouter than the ALB.

Anyone have a clue on what Beetle that ran into me this last weekend? Or website I can try? Pics would help. :)

Thank you


ALB is not known from California... you need not consider that one. As to what your beetle is, there are no species of beetle in North America that approach the size you've given. I suspect you may have seen either Prionus californicus (max length ~2.5 inches) or Derobrachus hovorei (max. length ~3 inches).

well, he was a cool bug, if a bit menacing, thanks for the info about him! my family and I arent too happy that skunks like to eat them though, because we have tons of skunks that love to spray near our open windows at night :) I'm also glad to know that he wont be killing any of my trees!


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