Stone Centipedes

2022 April 16

On April 10, 2022, I set out a little “pit trap” in the flowerbed next to our back door. This was a plastic cup, buried so that its lip was even with the surface of the soil, with a plastic plate propped up over it to keep out rain while still allowing small critters to run underneath and fall into the cup. The next day, on April 11, one of the things I found in it was this tiny little centipede. It was only about a quarter of an inch long. Fast, too. I put him in a white ceramic bowl that had slippery enough sides that he couldn’t crawl out, and he ran around and around and I occasionally snapped pictures of him as he ran through the focal point of the camera.

At higher magnification I couldn’t get all of him in the frame, so here is a closeup of his head,

And one of his tail.

I’d like to note that he has 12 pairs of legs (24 legs total).

So then I set out the trap again, and the next day (April 12) had caught another centipede that appears to be the same species, but is more mature. This one also ran around constantly, and it didn’t quite fit in the full frame, so here is a picture that at least shows all of its legs.

This one had 15 pairs of legs (30 legs total), so it had 6 more legs than the little one did. This doesn’t mean that they are different species, though. I am pretty sure they are both Stone Centipedes, Lithobius forficatus,[1] based on the fact that they have more than 25 antenna segments,

and also have little projections on segments 9, 11, and 13 (only segments 11 and 13 can be seen in the picture)

And, looking up Lithobius_forficatus, I see that this particular species of Stone Centipede hatches from the egg with only 7 pairs of legs (14 total), adding another pair of legs each time they molt until they reach adulthood with 15 pairs (30 total). So, that first little one had three more molts before becoming a mature adult.

Getting back to the big one, It was hard getting clear pictures of the head while it was running around,

so I ended up holding it between my thumb and finger for closeup shots. These are pretty rugged little beasties, so there was no real danger of me squashing it. We can see from the side that it had compound eyes, but with only a few dozen individual units rather than the hundreds or thousands that a lot of insects might have.

You can see some pretty muscular-looking appendages just below the head, ending in black spikes. These are the “poison claws” that they use to grab and kill prey.

As menacing as these claws look, it wasn’t able to stab me with them (although it sure tried). The skin on my fingertips is pretty thick, so if it had gotten hold of me someplace where my skin is thinner I might have felt it.

The poison claws aren’t part of the mouth, though. They are on the segment behind the head. The mouth is actually pretty tiny and hard to see. I can’t really tell if they can chew up their prey, or if the have to inject digestive fluids into it and suck up the juices.

This is actually an imported European species, but they certainly do well here. As predators, they help eliminate things like slugs and cutworm, so if you see them in your garden, don’t worry about them.


[1] While there are thousands of species of centipedes in the world, we only have a couple that live up here in upper Michigan. This is probably because they would have had to walk or be carried here in the 8000 or so years since the last Ice Age ended, and they mostly haven’t had time to walk this far yet. This particular species likes to hide in little crevices and can crawl pretty fast, so they probably got carried here by human activities before other centipede species could make it. So, I can be pretty confident that this is actually Lithobius forficatus, because none of the species that look similar to it have yet arrived in the area.

One Response
  1. April 25, 2022

    Those eyes look like Someone hollowed out a shallow divot and then just poured eyes into it until the excess eye rolled out and onto the floor. One of the creatures from God’s Lazy Period.

    “What? I gave it eyes! It’s got a bunch of them. No, I don’t know how many, I just filled the container. Whatever. Now it’s Celestial Miller Time.”

    Great photography as always, amigo.

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