Xystodesmid Millipedes

Apheloria virginiensis corrugata, a Xystodesmid Millipede from Great Falls, Virginia

Xystodesmid Millipede on top of a Spirobolid Millipede from Linden, Virginia

     Millipedes are invertebrates which feed mostly on decaying vegetation, fruits, and other detritus. As their names suggest, they have many legs, though not quite a 1,000. They have 2 pairs of legs for each of their body segments. Their bodies are usually long, round, and they frequently curl up when threatened to protect their softer underbellies and legs using their hard exoskeletons. They are often confused with predatory centipedes which differ in having only one pair of legs per body segment, flatter bodies, and being fast moving.
     Xystodesmidae is a colorful family of millipedes with an interesting defense. They secrete cyanide. They warn potential predators of this with bright colors. The cyanide also has a peculiar smell of almonds. Not everyone can smell them, but most people are genetically predisposed to do so.
     If you find a Xystodesmid millipede, gently pick it up and it will start to secrete the cyanide. The more it is disturbed, the more it releases. If you then take a sniff of one, you will likely be rewarded with the smell of almonds. This is not dangerous, although some sources recommend not rubbing your eyes or otherwise ingesting the toxins. I have never had any issues with them and have used this naturalist trick on many a field trip participant without ever having had any issues.
     So the next time you see one of these creatures, stop and smell the roses, or in this case the almonds...