1.Haemagogus janthinomys has been shown to retain the Asibi strain of yellow fever virus in its body for at least two weeks without exception, but in only one of six attempts did it transmit the virus by bite.
2.One specimen of Haemagogus uriartei retained the M. A. J. strain of jungle yellow fever virus in its body but was unable to transmit it by bite.
3.Owing to the short life of these mosquitoes in captivity the interval between the infection and the testing of them was not extended beyond sixteen days. The significance of this limited incubation period is discussed.
Included in this paper are experiments completed by N. C. Davis in this laboratory shortly before his death in 1933 and here published for the first time.