The mosquito, Aedes trivittatus, when fed through a membrane a trivittatus virus dosage of 103.4 to 105.5 suckling mouse LD50/0.03 ml of blood, transmitted the virus to suckling mice. Virus multiplication indicative of a biological vector occurred in this species. When Aedes vexans and A. triseriatus ingested similar dosages of trivittatus virus, both the infection and transmission rates were low and virus multiplication was poor. These results, added to evidence based on virus isolations from mosquito populations in nature, indicate that A. trivittatus is the primary vector of trivittatus virus in the north central United States.
Present address: Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D. C. 20012.