The biology and mating behavior of the pterygosomid mite, Pterygosoma mutabilis Jack (1961), was studied. Mite colonies were maintained on the lizard host in the laboratory. The active stages (larva, nymph and adults) fed on the host s blood. All developing stages, including quiescent ones, spent their entire life beneath the scales of the host; however, the commonest and longest-lasting stage was larva. Distribution on host body was indiscriminate. Nevertheless, immature stages preferred the venter, while adults favored the dorsum. Eggs were deposited singly and were found at random on the sand of the cage. Duration of stages at 80-90°F: Egg 7-9 days; larva 19-21 days; larval chrysalis 10-12 days; nymph 7-12 days (including nymphochrysalis); adult female 25-30 days. Males lack a nymphal stage; their life span was not determined. A complete generation lasted 68-84 days. The mating behavior of a mature male and female was observed in the laboratory. The male uses a spermatophore in fertilizing the female.