Hardwood Stump Borer

big beetle in my stump
Location: Miami, FL
May 3, 2011 7:00 pm
Hi there,
I’m a longtime fan, first time emailer!
I live in Miami, FL, and I have a big rotting stump in my yard (it was there when I bought the house; I don’t know what species it was). Last week my nephew noticed a pair of very large (~2” long) black beetles emerging from it. Since then, I’ve noticed that they emerge every day, right before dusk. I have found similar beetles on bugguide.net, but none with these exact feature. Can you help? Thanks! Note: in the photo, my beetle is covered in sawdust from a hard day’s work of stump-boring.
Signature: Jennifer P

Hardwood Stump Borer

Dear Jennifer,
Welcome to the ranks of the active contributors to our website.  We hope this is not your last submission.  This is one of the Prionid Root Borers in the subfamily Prioninae.  We believe it is the Hardwood Stump Borer,
Mallodon dasystomus, and here is the link to the Bugguide species information page.  Adult Prionids have very strong mandibles that are needed to gnaw their way out of the galleries they excavate in tree stumps and roots as larvae.  While they are not aggressive nor are they considered dangerous, their mandibles would most likely draw blood should they be carelessly handled.

Dear Daniel:
Thanks so much!  I love your website.  Thanks for providing such a wonderful service to the bug-curious people of the world.

2 thoughts on “Hardwood Stump Borer”

  1. Could you tell me what the adult stump borers eat? I’ve seen sites claim they are predatory, but that goes against the general wood boring beetle lore.

    • According to BugGuide: “Larvae bore in live heartwood of trees, incl. oak, elm, willow, pecan, maple, sycamore, etc.” There is no information on the diet of the adult. It is possible they do not eat. They are definitely NOT predatory.


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