Millipedes vs. Centipedes

A cute little millipede I saw at Little Bradley Falls, NC: the same hiking trail as last week’s granddaddy longlegs

Centipedes aren’t the worst arthropods around, but compared to millipedes they’re less than desirable – at least that’s my opinion, and what I presume to be the opinion of my fellow backyard bug hunters.

In elementary school, my friends and I would spend our afternoons roaming the school grounds moving rocks around in search of our shy millipede friends. We learned how to find them in the first place thanks to my amazing first grade teacher – she was the one who showed us where they hid and how to hold them gently. Our hands always smelled funny afterwards, but it was definitely worth it: you have not experienced true joy until a millipede has crawled through your fingers.

Centipedes, on the other hand, have caused me nothing but grief. I tried looking for millipedes in my yard many times when I was younger, and you know what I found? Centipedes. Angry, biting, writhing centipedes. I mean, I could usually find some ants and mulch lobsters (roly polies, for those new to the blog), and those were pretty cool, but there was always at least one feisty, orange chilopod that I had to avoid while trying to pick up the friendlier arthropods.

You’ve probably started thinking “okay, we get it, millipedes rule and centipedes drool, but what are the biological differences between the two?” Fortunately, I can elaborate on this question of yours thanks to my semester in good ol’ Biology 102.

I know, I know, one generic class on animals isn’t enough to make me an expert, but I also have Google at my fingertips so I used that to fill in the blanks in my knowledge as best I could – the interesting blanks, at least.

Anyway, centipedes and millipedes are both members of the group Myriapoda and are recognized by their many legs, long bodies and fondness for dirt. Besides body structure and preference of living space, however, centipedes and millipedes actually have very little else in common.

While millipedes join the ranks of the detritivores in your compost bin, centipedes are ruthless predators that kill their prey with a toxic bite or venomous sting. These bites and stings are not particularly dangerous to people unless one is allergic, but I think it’s safe to say we’d rather them copy the millipede’s defense mechanism of rolling into a ball instead.

That strange odor that got on our hands in first grade is also part of a millipede’s efforts to deter predators, so maybe they didn’t quite enjoy our presence as much as we did theirs.

The name “millipede” literally means “a thousand legs.” While millipedes have more legs than centipedes at four per body segment rather than two, they usually have only several hundred or less than one hundred in total. The centipede name means, surprise-surprise, “a hundred legs,” which is actually pretty accurate depending on the species. Centipede legs and antennae are generally much longer than those of millipedes, but overall millipedes are generally larger than centipedes.

While the traditional organism is typically black, brown or reddish, the millipedes I played with were yellow spotted millipedes (also called almond-scented millipedes for good reason), which were brown with yellow dashes running up their sides and were flatter than most common millipedes. A few fun facts about these cute little diplopods: their colors get brighter as they age, they get longer as they grow older by adding an additional body segment every time they molt, and that almond scent comes from cyanide.

Yes, cyanide. Fortunately, millipedes are too small to actually harm people with their toxic chemicals, but still – these unassuming little dudes are secreting genuine cyanide from their bodies. They’re immune to it, but most of their predators obviously are not, so… yeah. Honestly, after all the wacky things I’ve learned about animals with exoskeletons in my brief time researching for The ArthroBlogger, tiny animals partaking in chemical warfare doesn’t even phase me.

Another fun fact about millipedes is that you can often tell males and females apart. If you flip a millipede on its back and it’s missing its seventh pair of legs, or those legs are shorter than the rest, it’s probably a male. This is because those “legs” are actually gonopods, which are used in mating.

When a female millipede is ready to lay her eggs, she’ll dig a hole to lay her eggs in. Millipedes are just like sea turtles in this sense, laying a hundred or so eggs in the ground before wandering back off into the great unknown – except I’m pretty sure sea turtles don’t nestle their eggs in their own poop, while millipedes…

Anyways, time to get back to centipedes. The centipedes I’m most familiar with are the tiny orange ones I would always find under steppingstones in my yard scaring away all the mulch lobsters, but I think we all know about the infamous house centipede. If you don’t, allow me to get the two of you acquainted:

House centipedes have thirty insanely long legs that basically look like living hairs sticking out of their sides. This makes them kind of funny to look at, but what is a bit worrisome is that those front two “legs” are actually what the centipedes use to sting their prey. Like millipedes, these guys aren’t dangerous enough to send you to the hospital or anything, but that doesn’t mean getting stung wouldn’t hurt.

As long as you stay away from them, however, house centipedes make pretty good roommates. These hangry chilopods eat termites, spiders, cat beetles and other unwanted pests by catching and killing prey with their crazy legs – they pounce on and “lasso” unsuspecting insects, or simply use their long limbs to beat the bugs to death.

Yeesh. Glad they’re on our side.

Renaming time: I love the “almond-scented” nickname for yellow-spotted millipedes, but to encompass as many of the thousands of millipede species as we can in a single term, I think we ought to just call them “cocoonapillars,” since they look like caterpillars that started making a chrysalis and then gave up halfway through (I mean that in the nicest way possible). While the centipede name fits pretty well, I think they’re better off as “pedepedes,” because it emphasizes their crazy legs and sounds hilarious when you say it out loud.

Seriously, this blog is a major breakthrough in the field of taxonomy. In a world where arthropods already get names like Agra cadabra and Pieza kake, the names I’m making up aren’t too shabby.

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