The Yellow Spotted Millipede

The Yellow-spotted Millipede lives in moist forest floors along the Pacific Coast of North America from California to Alaska.

Mating occurs mostly in the spring and several hundred poppy-seed sized eggs are laid clustered loosely in soil or leaf litter. Young millipedes are paler in color than adults (light grey body with pale yellow spots) and have fewer body segments (and less legs). Each time they shed their skin, they add a segment and become a slightly darker shade of grey and have slightly brighter yellow spots. Once are they are about 4 to 5 cm long, 0.75 cm wide with their black and yellow colors, they are mature and are able to reproduce. At this point they have about 20 segments and females have 31 pairs of legs (14 double pairs and 3 single pairs) while males have only 30. The 8th pair of legs from the back on adult males appear to be missing. The leg pair is actually there, but modified into a gonopod for sperm transfer. You'll need magnification to see it. Yellow-spotted millipedes live to about 2 to 3 years of age.

They are not eaten by many creatures because they can protect themselves in two ways. The first is to curl its body into a tight ball, ressembling a snail with the hard exo-skeleton protecting its back. The other way is to release a smell from small pores in each segment which can kill or scare off other small creatures. To humans, this smell is pleasant and smells like almond extract. But to small creatures such as beetles and shrews, the smell contains the chemical cyanide, which is toxic to them in very small dosages.

Like most animals that bite, sting, taste bad or smell bad, yellow-spotted millipedes have a warning coloration. The bright yellow spots on a black background serve to warn potential predators that they can protect themselves, much like a yellow and black paper wasp warns that it can sting. If a small animal survives a meeting with this millipede, it will avoid it next time it meets one. Interestingly, all other millipedes (of the same species and different species) seem to be immune to this toxin.