Dermacentor andersoni, commonly known as the Rocky Mountain wood tick, is a species of tick. It can cause tick paralysis. This tick is well known as a vector of the Rocky Mountain spotted fever rickettsia in the northwestern U.S. and Canada, the Colorado tick fever virus, and the bacteria which causes tularemia (hunter's disease).Diagnostic features: The larva only has three pairs of legs. The nymph has four pairs.