The Microsporidian parasite Pilosporella fishi Hazard and Oldacre, 1975 was described from larvae of Wyeomyia vanduzeei Dyar and Knab, collected from leaf axils of the bromeliad Tillandsia utriculata L. The collection locality, near Vero Beach, Florida, is the site of a study area where a population of Wy. vanduzeei has been monitored since 1973. The parasite causes much greater mortality of female than of male immature Wy. vanduzeei. The low incidence of infected larvae in the mosquito population suggests P. fishi is of little importance in regulating the population of Wy. vanduzeei.