What's That Bug? does not endorse extermination

Subject: What is this beetle?
Location: San Diego county
September 16, 2013 6:49 pm
My sons call this a rock beetle but I don’t know what it is really called. Found in September in inland San Diego County. They find them in the grass, near rocks. They would also like to know what it eats.
Signature: Wants to impress my boys

Ironclad Beetle

Ironclad Beetle

Well, we will do our best to make you shine.  This is an Ironclad Beetle in the genus Phloeodes.  According to BugGuide, there are two species in California, Phloeodes plicatus and Phloeodes diabolicus, and the latter has the common name Diabolical Ironclad Beetle.  Most of the information is contained on the BugGuide information page for the Diabolical Ironclad Beetle where it states the habitat is “Woodlands, Found under loose bark of oak, cottonwood.”  There is no information provided on diet.  We turned to Charles Hogue’s Insects of the Los Angeles Basin where the author writes:  “This beetle derives its name from its extremely hard body wall, which may be difficult to pierce even with a sharp pin.  …  Adult Ironclads are fairly abundant locally under the loose bark of dead trees, especially oaks.  They are thought to feed on punky fungus-ridden wood.”  The Sam Wells Bug Page has some interesting information, including:  “Ironclad beetles are the tanks of the insect world. They are famous (or infamous) for walking away after being stepped on. There are even reports of species being run over by cars without apparent harm. To an entomologist, they are notorious for the challenge of getting an insect pin through their thick skin (cuticle). What usually happens is the first attempt bends the pin. The second attempt bruises the thumb and forefinger to the bone. And then with a combination of anger and grit (and with two hands gripping the shaft) the pin is forced through the reinforced exoskeleton. With luck it has gone through straight and without popping the legs off on the other side. Very often it doesn’t – as verified by any number of oddly pinned specimens stuck to the bottom of unit trays in the museums of the world.”  We imagine your sons refer to them as “rock beetles” because they are as tough as rocks.

What's That Bug? does not endorse extermination
Location: San Diego, California

7 Responses to Diabolical Ironclad Beetle, we presume

  1. Roger Fuester says:

    Interesting article.

  2. Jason says:

    Found one at a customers house.
    Thanks for the info, never seen one before.

  3. Maggie says:

    My daughter brought one home, but we don’t know what it eats. Appears to go for the mushroom. Sure would like to know what else. Not sure how hard it is to find lichen covered tree bark. Please give us ideas if you have any. Thanks!

  4. Eleanor Osgood says:

    Recently found one in the restored coastal sagescrub/chaparral habitat of Baldwin Hills in Los Angeles in wood chip mulch near a young oak tree

  5. Aprilynn Wyatt says:

    We have many iron clad beetles on the cenral coast. Oak woodlads and chapperal. In Prunedale ca an hollister ca we see them.

  6. Jennifer says:

    We just found one in the sand we live in Woodward, Oklahoma in the northwest part of the state. We have no trees it’s just flat plains here.

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