Small millipede with spots

2011 January 15

Well, I see I’ve been neglecting the myriapods again, so here’s a millipede that Sam found back in 2008, on May 10. It was under a rock next to the house, and it is fairly small (only about 14 mm long).

Millipedes have four legs per body segment, compared to only 2 legs/segment for centipedes, and I’m counting about 44 segments here, so this one looks to have somewhere around 176 legs (give or take a couple of groups of 4). This is way more than we were seeing on the soil centipedes, and this isn’t even a particularly long millipede as these thing go.

They aren’t particularly fast, and are easy to catch. The body has a hard shell, though, making them feel like a piece of metal wire when you pick one up. When they curl up to protect their relatively delicate legs they are pretty rugged.

Millipedes are generally herbivores or detrivores, rather than being carnivorous like centipedes. They don’t have obvious defenses against being eaten other than being hard, but there is something that is not immediately obvious; see those spots running down its sides, one spot per segment?

Those are defensive chemical glands. Millipedes have excellent chemical defenses to keep from getting eaten, as shown by this match between a house spider and a small millipede. The specific chemicals vary depending on what kind of millipede it is, but some of them produce hydrogen cyanide gas, which is right up there on the nastiness scale. Since the chemicals take a bit of time to work, the millipede has to be rugged enough to take the initial abuse, but most predators will give up before they do any really lasting damage.

It looks like the cylindrical-bodied millipedes are mostly in the order Julida, but after that identification gets difficult. And there don’t seem to be many millipede experts on BugGuide[1]. This one is probably one of the Parajulidae, which are the dominant native millipedes in North America. Although, it is probably not the same species as this millipede that I posted earlier, which does not have its defensive glands showing up as clearly visible spots. And for that matter, it could be one of the Blaniulidae, which seem to be more definitely spotted than most of the other millipedes.

[1] It appears that BugGuide has an adequate number of experts for insects, but I think they could use more people who specialize in non-insect arthropods like millipedes, pseudoscorpions, spiders, and similar creatures. There seem to be a lot more of these posted than there are people able to tell what they are. Of course, I understand that these are often harder to ID from photographs than are a lot of insects, so even if there were more people specializing in them, they might not be able to do much with them on BugGuide.

6 Responses
  1. Anne Bingham permalink
    January 15, 2011

    I cannot believe I just spent time on a Saturday morning double-checking your count of the millipede segments and watching the spider-millipede smackdown!

  2. January 16, 2011

    The real burning question is, did you get the same number of segments as I did?

  3. Anne Bingham permalink
    January 16, 2011

    Um, I got 45. But the results are not publishable because I didn’t repeat the experiment to duplicate the results, the experiment was not peer-reviewed, and the technique left a lot to be desired because I was looking at a second-generation print and trying to avoid touching the screen because I detest laptop screens that are coated with smudges (and worse).

  4. January 16, 2011

    I counted and got 44. Though like Anne alludes, I’m too sick of counting segments to repeat the process.

    So centipedes will bite, and millipedes will not? I always thought it was the other way around. Maybe I always thought “more legs = dangerous” for no justifiable reason. Though now that I look at pictures, centipedes look a lot meaner. So predators have to decide between a hydrogen cyanide attack versus poison venom? And people say nature is beautiful?!

  5. January 17, 2011

    I appreciate the segment counts, it really is surprisingly difficult to count them without losing track at some point. As far as biting, I’ve had millipedes kind of try to abrade a hole in my skin, but their mouthparts are more suited to scraping than to biting.

    As far as the danger goes, it could be that the gas attack of the millipede is, in fact, more hazardous than the venomous bite of the centipede. Come to think of it, a lot of vegetarian animals are more dangerous than the carnivores – I understand more people are killed by moose than by wolves, for example, and I recall being told that the most dangerous animals in Africa are the Cape buffalo and the hippopotamus. And in the arthropod world, I think honeybees kill more people than, say, scorpions or venomous spiders.

  6. January 18, 2011

    I didn’t count segments, but I did read about the battle with the spider. Great stuff as always! Looking at your photos made me wonder about the mechanical engineering aspects of the legs.

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