Millipedes are arthropods (jointed bodies and legs, no backbone) belonging to the subphylum Myriapodia (many legs). Millipeds are not insects or aradchnids (spiders) but are more closely related to lobsters, shrimp and crayfish. Worldwide there are over 10,000 species of millipeds. “Millipede” in Latin means “1,000 legs”, a misnomer because the millipede with the most legs only has 750 pair.
Millipeds are scavengers, feeding on decaying vegetation and leaf litter and preferring moist habitats with high humidity. They are most active at night. The wormlike body of a millipede is composed of rounded segments, each of which has two pairs of legs, which are in line with the body and do not extend out to the side. Only the first three segments of a millipede break this pattern and have one pair of legs. The head of a millipede is round and has short antennae. Breathing is accomplished through little holes or spiracles on the sides of the body. Females are larger than males. Millipedes spend most of their lives in the soil and can easily burrow.
When threatened, millipedes curl their body into a spiral to protect their soft undersides. Many species also have glands that produce irritating fluids as protection. Some of these fluids contain hydrochloric acid or are allergenic to humans.
In spring millipedes lay eggs in the soil. After a few weeks the eggs hatch. The young at first only have three pair of legs and seven segments or less. With each molt, more legs and segments are added until maturity is reached in two to five years. Millipedes live several years after reaching maturity.
This millipede was photographed at Burney Falls State Park (Shasta County CA) along the Rim Trail. There are seven species of Tylobolus millipedes in the West. Members of this genus are reddish brown to black in color. The posterior margins of their segments are faintly or boldly colored red to yellow giving Tylobolus millipedes a striped appearance. Based on range (Northern California, Washington and Oregon) I believe this specimen is Tylobolus uncigerus, the most northernmost Tylobolus millipede.
Narceus americanus, is an eastern millipede that closely resembles Tylobolus species but does not occur in the West.