European Ground Beetle

2011 July 2

Sam and I were turning over rocks on August 1, 2010 and found this fine, large beetle. Those are my fingers it is crawling over, which makes it about an inch (2.5 cm) long.

It is very similar to a beetle that I previously posted back in 2007, and tenatively identified as Calosoma calidum (although, I see that it has evidently been renamed Callisthenes calidus since then). Except, that one had distinct gold-colored dimples on its wing covers, while this one has very little coloration in the dimples. At first, that made me think that what we had here was the related Calosoma frigidum.

But, on closer inspection, I see that the pronotum (the shield covering the segment that the first two legs come out of) is shaped completely wrong for either of those. Instead of tapering down to a neck, it has iridescent flanges on either side that project back over the shoulders. Here’s a comparison: the top beetle is the beetle I had posted previously, and the bottom one is the one we are looking at right now:

On due consideration, it looks like a better candidate is the European Ground Beetle, Carabus nemoralis

Huh. Yet another non-native beetle. They have evidently been introduced (whether on purpose, or by accident) on both the east and west coast, and have been working their way towards the center of North America from both sides. Wikipedia says that they are common not only in Northern Europe, but also in Iceland, and are generally regarded as beneficial because they eat Gray Garden Slugs. This is why I think that they could have been introduced intentionally, although their habit of burrowing into soil and under rocks would have also made them likely to be accidentally introduced in ship ballast.

These are active hunting beetles that evidently particularly like slow-moving invertebrates that they might find in the grass or under rocks. I expect that they are also prime predators of the many species of cutworms that we seem to have in some abundance around here. Their legs are strong enough to let them wedge themselves under rocks, and long enough to let them run fairly quickly.

And, once they catch something, those jaws are no joke. It looks like it could hack a caterpillar into bite-sized chunks with no difficulty whatsoever.

If it is like the related Calosoma species, then it could live for a couple of years as adults, so from a standpoint of longevity they would make perfectly good pets. Caterpillars to feed one might be a bit hard to come by in the winter, although the waxworms that the local bait shops sell for ice fishing would probably work fine. For that matter, I suppose that one could maybe just put one in a jar with some moist soil, and stick it into the refrigerator to hibernate over the winter.

Or just let it go for the winter. That would probably be better.

5 Responses
  1. July 2, 2011

    Your site is a WONDERFUL concept. With the obscene prices of fuel, I’m certainly thinking about limiting my “bug travelling”, and concentrating on “The Fauna of Puncheon Camp Creek Hollow, in Douglas County, Missouri”. I have twenty acres, and could probably spend the rest of my life just trying to discover what’s living here. Thanks for a great read, ALL the time.

  2. July 3, 2011

    Thanks, George. It really is astounding just how many kinds of insects there are in the average yard, and you’re right that it is way more convenient to just step outside and start rummaging than to travel long distances looking for something specific. What’s really amazing is if you walk into a patch of tall grass, with no obvious insects, and then just run a sweep net through it for a few strokes. When I do this, I generally end up with probably 100 insects in at least a dozen different species after just four our five sweeps.

  3. Jesus permalink
    September 10, 2011

    Thanx I’ve found a few of these in the backyard this summer. Good to know they eat slugs there have been lots of those this summer.
    To give an idea of the “invasion” of this insect I live in Edmonton Alberta Canada.

  4. Valerie W. permalink
    June 1, 2013

    We’re trying to figure out what type of beetle(?) we’ve been finding in the barn our horse is boarded in. They are black, or very dark in color, & are about 1 inch or so long, kind of slender, & we find them crawling around in the wood shavings used as bedding in the stalls, &, in the horse’s grain bucket if the horse isn’t in his stall when they put the grain in his bucket, & floating in the horse’s water buckets. I’m guessing some sort of ground beetle, or ? We live in Missouri, the barn is near Fenton, & we want to make sure they’re not harmful. Thank you!

  5. June 2, 2013

    Valerie: Your beetles sound like some kind of darkling beetle. Since they seem to be associating with grain, they could be mealworm beetles, the adult form of the mealworms that are commonly sold to feed pet lizards and the like.

    There may be a neglected pile of grain in some corner of your barn where they are breeding. They aren’t particularly harmful, as long as they don’t get into grain that is being stored for long periods of time. And even if the grain is infested, the larvae aren’t toxic and your horse is probably OK with eating them.

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