They are often referred to as almond, or cherry, millipedes. The reason? Pick one up and give it a shake inside your balled up fist. The millipede will exude a very pleasant aroma, quite reminiscent of one of the aforementioned fruits. People always react favorably to this fragrance. It apparently is the result of the animal releasing benzaldehyde when under duress, possibly as a form of predator deterrence.
As can be seen in this macro photo, a millipede has two pairs of legs per body segment, and like most millipedes the body is long and cylindrical. Millipedes move in a slow, graceful gliding motion, and are easily captured. They're herbivores, feeding primarily on decaying plant matter.
Centipedes have one pair of legs per body segment, and in general possess far fewer legs than do centipedes. For the most part, they appear leggier and move far faster than than their sluggish millipede brethren. They tend to look much more "creepy" than do millipedes. Also, centipedes are predatory carnivores, armed with venom-producing glands to help disable victims. Some species can deliver a painful bite
But no worries with mild-mannered plant-eating millipedes. In fact, at least the Sigmorias smell delicious.