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Millipedes (Class Diplopoda) are elongated, multi-segmented myriapods. The segments are hardened and in cross-section form a complete ring in some species. In others, they form a dome that allows the millipede to roll up into nearly a perfect ball. Each segment has two pairs of jointed legs. The name millipede means 1000 legs. The largest number of legs any diplopod possesses, however, is 375 pairs, for a total of 750 legs. They are generally short and seem to move in waves as they propel the millipede slowly forward.

Some species have a single eye (ocellus) on each side of the head, but some have 90 ocelli per side. The soil dwelling types have no eyes. They have one pair of short, elbow jointed antennae responsible for the sense of touch and smell. They are necessary for a millipede’s survival. They are vegetarians, feeling on living and dead plant material.

There are approximately 8000 millipede species. Some of the smallest are only a tenth of an inch. In contrast, the largest are almost a foot long. One of the United States Southwest’s largest millipedes is this long.

Millipedes occur most commonly in temperate and tropical regions. Those species which inhabit arid regions have special physical and behavioral adaptations which make it possible for them to survive. Their thick, waxy exoskeletons inhibit water loss and they can be dormant during long periods of severe heat or drought.

Despite the number of legs, most millipedes move slowly. They can be found under wood, rocks and decaying vegetation.

Millipedes mate when the summer rains begin. The female stores sperm until she is ready to lag her eggs. She lays up to 300 eggs, fertilizing them as they are laid in the nest made of soil and fecal matter. Newly hatched millipedes have 3 sets of legs. With each molting, there are more legs. The skin casts from the moltings are eaten. They molt as many as 15 times. Millipedes live up to three years.

Millipedes have two glands per segment, one on each side, each producing irritating chemicals. When disturbed, the millipede ejects droplets of this secretion through special pores which deter predators such as spiders and lizards. In humans, the secretion can cause blistering of the skin and burning if rubbed in the eyes. Washing the skin helps. If the problem persists, see a physician.