The dispersion and flight range of forest mosquitoes were studied in a preliminary investigation to determine the role of these insects in the spread of the virus of jungle yellow fever over open country between forests. Sylvan mosquitoes were marked with bronzing powder and released in a small wooded area near Passos, Minas Gerais, Brazil. Recaptures were made after 12 hours, at the point of liberation and in neighboring forests, up to a distance of one kilometer. Nine per cent of the Haemagogus spegazzinii, 50 per cent of the Aëdes leucocelaenus and 16 per cent of the other marked species were recovered, the last specimen being taken on the twelfth day after release.
In another experiment, on flight range, Haemagogus spegazzini and Aëdes leucocelaenus were not available in large numbers, but an experimental vector of yellow fever, Aëdes scapularis was recovered at a distance of more than four kilometers, and 11 days after release in the forest. Other mosquitoes recaptured at distances of more than one kilometer from the point of liberation were Aëdes serratus, Psorophora ferox, Aëdes crinifer, Chagasia fajardoi and an anopheline.