Beetle larva, probably predatory

2009 October 31

Last Sunday, we found this larva in a corner of Sam’s dresser drawer. It was pretty hard to catch, it could run quite fast and could easily squeeze down into small crevices in the wood, but eventually I got it into a small plastic container and got it up to the camera.


Of course, once there it kept scurrying around and around and around. Eventually, I got tired of chasing it, and left it for a while to calm down before trying again. “A while” turned out to be a couple of days, and when I got back to it, it was all contracted and looked like it might have died from lack of moisture.


Then I saw it moving, so I thought I’d give it a bit of water to recusitate it. At which point, it woke up, streched out, and started scurrying around again. So I got some more pictures as best as I could, particularly of its head


The mandibles were not huge, but not tiny either. The speed that it moved leads me to think that this is something predatory, not some slow-moving grazer like a carpet beetle. It is clearly a beetle larva, what with the well-developed true legs, the lack of any prolegs, and the distinct mandibles, but that doesn’t narrow it down much.

Based on the pretty solid-looking urogomphi (the projections on the tip of the abdomen), it looks kind of like it might be the larva of one of the rove beetles in the family Staphylinidae, but there are a lot of different kinds of rove beetle. If anyone has a suggestion to narrow it down, I’m all ears.


And just a few minutes ago, Sam brought me another one that she just found in her room. I also saw one in a bucket in the garage a couple of days ago. Hm. This could be a sign of a problem: if I’m right and they are rove beetles, then while they wouldn’t be eating, say, our clothing themselves, they might be eating other things that are pests – implying that these other things are around to be eaten. And if I’m wrong about what they are, they might actually be pests in their own right, eating things that we don’t want eaten. I should probably try raising them to adulthood to see what we get. If successful, I’ll be coming back to these later.

***Update*** I kept the larva in a small plastic container and periodically gave it pinches of moist potting soil from our houseplants, which it survived on OK. It ultimately pupated in the last week of January, and emerged on February 1 as a (drumroll please . . . ) Scarlet Malachite Beetle!. Not quite what I was expecting, but that certainly answered that question. Of course, now the second question is, what was it doing in the house? Then again, in my previous post about them, I noted that they are known in England for living in thatched roofs. So, maybe they do have some proclivity to join the house fauna.

6 Responses
  1. Ellen permalink
    October 31, 2009

    Hm…well, good luck. I’ll be interested to see what turns up if you raise them to adulthood.

  2. November 2, 2009

    Raising them to adulthood would give you a chance to do a photo series on growth and development. It could be cool.

  3. November 2, 2009

    I just hope I can keep them alive. I suppose some moistened leaf litter is likely to have the sorts of things they like to eat in it (either other bugs, or decomposing plant matter).

  4. November 3, 2009

    So far, so good. I have them in a small container, and gave them some moist potting soil from a houseplant (which, on close inspection, turns out to have little bugs crawling in it – springtails, I think). They immediately started crawling all through the soil, looking like they were hunting. I hope they are successful.

  5. February 4, 2010

    It finally turned into an adult this week. It turned out to be a Scarlet Malachite Beetle. So, I was right about it being predatory, but a bit off on it being a rove beetle.

  6. ehteshami permalink
    July 10, 2010

    i think it’s the Dermaptera

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