Beetle Development – Rearing a Scarlet Malachite Beetle Larva

2010 February 13

Previously on “What’s That Grub?”
Back in October, we found this larva in Sam’s dresser drawer:

At the time, I didn’t know what it was, although we guessed it was something predatory based on the way that it moved. It was pretty clear that identifying it would require raising it to adulthood, so I put it into a small plastic baby-food container, poked a couple of holes in the lid, and took a whirl at it.

The big question was, what do you feed to a grub when you don’t know what it eats to start with? I figured that, since it was probably something that hunted in leaf litter, there was a good chance that if I just gave it some reasonable simulation of leaf litter it would find enough of whatever it needed to get by. So, I gave it a pinch of moist potting soil from our houseplants every few days. This contains a lot of decomposing plant matter, and also has living things like fungus, fungus gnat larvae, and probably little guys like springtails and mites that I couldn’t actually see with the naked eye.

This seemed to suffice. Maybe it didn’t exactly thrive, but it did stay alive and gradually get bigger, until finally, around the last week in January, it pupated.

Unlike the pupae of butterflies, moths, and flies that I have seen, this one actually showed a lot of detail of what it was going to become.

It lasted in the pupal stage for about a week, starting out a nice pinkish brown color, and then darkening just before it emerged. And then, finally, the beetle came out. At first it just lay there and the colors were kind of subdued, but after about a day its wing covers turned red and green, it stretched itself out, I put down the container to find my camera, and – it promptly escaped through one of the holes in the lid of the container before I could commit photography. I’d gotten a good enough look that I was pretty sure of the ID, but geeze, no pictures . . .

I was pretty disappointed by this, since I’d gone through almost three months of tending this beetle and then didn’t have a chance to get a picture. But then, the next day, we were in the living room and Sam suddenly said, “Hey, there’s a beetle on the window![1]” Sure enough, it turned out to be the very beetle! This time, I got it under the camera before it could escape again, so that I could prove that it was this:

Hey, this is something we’ve seen before! Its a Scarlet Malachite Beetle!

Well, that’s a relief! These are predatory beetles that don’t much bother anybody, so we don’t have to worry about them, say, chowing down on our clothing or getting into the food in the pantry.

So overall, what did we learn?

1. So, *that’s* what a Scarlet Malachite Beetle larva looks like!

2. Simulated leaf litter is probably a pretty good media for raising most unknown beetle larvae, because it contains both detrius for the detrivores, and small prey items for the predators.

3. Anybody trying to settle down and raise a beetle larva had better be in it for the long haul, because even a tiny one can take a long time.

[1] In the months of January and February, I think that we’ve found three sizeable insects on the windows, and all three of them were things that we were raising from larvae to see what the adults looked like (the other two were waxworms).

5 Responses
  1. February 13, 2010

    Kids! You raise them, you care for them and then the first chance they get, they fly off, never looking back to even say, Thanks!”

  2. February 15, 2010

    Yep, and then they smack into the window . . . or, as the case may be, drive the car into the ditch.

  3. jkien permalink
    October 26, 2010

    Thank you for sharing this great work! Yesterday someone here in the Netherlands posted a picture of a similar red larva in his bathroom, wondering what it might be. We stumbled upon your blog on rearing a Scarlet Malachite Beetle Larva, so now we know the larva is a “roodtip basterdweekschildkever”.

  4. October 26, 2010

    jkien: Glad it was helpful! It looks like the “roodtip basterdweekschildkever” is a relative, but with more green on the wings. What does that translate to? Is it something like “red-tipped soft-shelled beetle”?

  5. jkien permalink
    October 26, 2010

    May be we aren’t completely sure about the green colors that ‘our’ larva will produce finally, but the “roodtip basterdweekschildkever” is a fair guess. Supposedly it is a common insect around here. The translation is red tipped bastard soft-winged beetle, so you are speaking Insect Dutch quite well!

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