Utah State University Extension
Millipedes are related to trilobites, spiders and ticks, sowbugs, and crayfish, centipedes, and insects. Each group represents a different class of arthropods. Millipedes or "thousandlegged worms" include over 800 species of the class Diplopoda in North America.
Karren, Jay B. and Roe, Alan H., "Millipedes" (2000). All Current Publications. Paper 1346.