Meet the millipede that uses cyanide as self-defense

March 14, 2019, 9:08 a.m.

This resident of forests in the Pacific Northwest is dainty, dotted and dangerous. Well, dangerous to small predators anyway.

The fancy yellow dots decorating the keels of this little millipede are more than just interesting coloration. Like many animals that use bright colors as a warning to potential predators, the yellow-spotted millipede is also doing a favor to hungry birds, shrews or other hungry insectivores. It's telling them in no uncertain terms that trying to eat it would be a mistake of lethal proportions.

If you were to pick up and handle this little critter, you'll likely notice the scent of toasted almonds. That's because the poison-packing millipede uses hydrogen cyanide, which smells of almonds, as self-defense. When threatened, it releases the poison in quantities large enough to be deadly to birds and rodents (but not strong enough to harm humans). All you'll likely feel is a mild stinging sensation on the skin of your hand, or if your skin is more sensitive, a burning and blistering sensation.

This millipede is an important part of the forest ecosystem, and a common resident. In some areas, there can be as many as 20 to 90 individuals per square meter, and, according to the Los Angeles Times, "in some studies, they comprise more than 30% of the total invertebrate biomass." That's a lot of millipedes! But each of them is necessary.

Consuming more than a third of all the needles that fall from conifer trees, the yellow-spotted millipede, "expedites the leaf litter's decay, breaking down cellulose and lignin in its gut and excreting ready-to-use fertilizer in its wake," says U.S. Fish & Wildlife Service. "Like earthworms, the millipedes provide an immeasurable benefit to the health of the forest, aerating soil, cycling nutrients, and generally keeping plant waste at a manageable level."

Beautiful, industrious and packed to the keels with poison — who could ask for a more intriguing arthropod to encounter on a hike in the woods of the Pacific Northwest!