These are primarily native to North America, and they occur throughout the United States.
Millipedes are slow moving vegetarians, feeding on both decaying vegetation as well as live plant tissues. They are essentially harmless to humans in North America, while some species in South America are able to exude a cyanide-like spray from their bodies when disturbed. North American species do exude an unpleasant smelling secretion, and they also may lose body fluids as they die, causing staining on indoor surfaces. The secretion is a combination of irritating chemicals that may cause skin rashes on people and even be toxic to small animals. The larger species are capable of living up to 8 years, sometimes requiring up to 5 years to reach sexual maturity. Eggs are laid in the soil in batches of from 20 to 300 eggs, and newly emerged nymphs are very small with only around 7 body segments and only 3 pairs of legs. As they grow they add more sections and legs. In addition to the foul odor they can give off, millipedes protect themselves by rolling into a tight coil when disturbed, protecting the more vulnerable ventral parts.
The larger millipedes are elongate and cylindrical, getting up to more than 4 inches in length. The smaller garden millipedes are usually less than ¾ inch long and are more flattened in appearance. They all have 2 pairs of legs on each body segment, differing from the centipedes. There is a pair of short antennae.
Characteristics Important in Control:
Habitat modification to remove the objects and debris on the soil that millipedes use for harborage is needed. These animals require areas of fairly high moisture, and reduction of unnecessary moisture also reduces the attraction of an area. Invasions of structures may occur when surrounding areas dry out in the summer, driving millipedes to the green, moist landscape around the structure. Treatment of the perimeter of a landscape, as well as the building perimeter, with a residual insecticide will help to kill migrating millipedes.