Both sexes of Toxorhynchites amboinensis, an unusually large, non-blood sucking mosquito, were found to be as susceptible to infection with each of the four types of dengue virus by intrathoracic inoculation as Aedes albopictus. Tx. amboinensis infected with dengue virus could be identified easily by fluorescent antibody staining of head squashes and had advantages of size, hardiness, and safety (for females) as compared with Ae. albopictus. Tx. amboinensis also were more susceptible to infection with Japanese and St. Louis encephalitis viruses than were Vero cell cultures and appeared useful for detection and propagation of other flaviviruses and arthropod-borne viruses of other taxonomic groups.