We also share jointed legs. The limbs of centipedes, millipedes and their distant kin, insects, spiders and crustaceans are moved by muscles attached to the insides of their crusty shells. In contrast, our muscles surround the bones. This difference limits the size a creepy can attain, and thank goodness.
We all have a digestive tube, which runs through from mouth to anus. And we all have one urinary system, although they excrete ammonia rather than urea. But where we have a single set of lungs, creepies have air ducts in each segment, which open through spiracles in their exterior cuticles. They also have a single (centipedes) or double pair (millipedes) pair of legs on each segment.
Both creepies have a waxy cuticle, which does not retain moisture, so they need to avoid sunlight and dry situations. They are most often found in moist habitats beneath leaf litter, rotten logs, or underground.
Centipedes, being aggressive carnivores, don’t have sexual intercourse: it’s way too dangerous. The male deposits a sperm-filled ball on the ground and hopes the female finds it. Once she takes up the spermball, she makes a nest in the soil or rotting wood, and lays the eggs, and fertilizes them.
Millipedes, being peaceful detritus-eaters, do enjoy conjugal bliss. Both sexes have genital pores on the third segment. The male uses his penis to transfer a sperm packet to a modified pair of legs, the gonopods, on the seventh segment. These put the sperm packet into the female during copulation. The female stores the sperm, and fertilizes the eggs with it when she lays them. After several weeks, young with only a few segments hatch. They will add more segments with each successive molting.
Centipedes are flat rather than round, and have large antennae and at the rear of the head one pair of large pincers. These are modified legs, which are used to capture prey and inject venom into the prey. The segments behind the pincers have legs, each posterior pair being longer than those in front, enabling the centipede to move rapidly without the legs colliding.
They hunt at night for soft-bodied prey of the right size, like earthworms and springtails. And they are prey to salamanders, beetles, spiders, snakes and even mice.
Millipedes are round-bodied burrowers, slow-moving on short legs, creeping along feeding on organic debris in the soil. They cannot bite or sting, so when threatened they coil up. When disturbed, glands in the segments release hydrogen cyanide gas. Our local millipede has distinctive coloration (black with yellow spots) to warn predators away.
Eve Broughton lives in Whitethorn and was educated at UC Berkeley.
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