There are recorded here the distribution, the annual cycle of abundance, the vertical stratification in the forest, and the possible relationship of the forest mosquitoes attacking man to the transmission of sylvan yellow fever following an outbreak of this disease in Panama. Particular attention is directed toward species of mosquitoes which are proven vectors of sylvan yellow fever in South America, Haemagogus spegazzinii falco and Aedes leucocelaenus.
Haemagogus equinus and H. lucifer proved to be considerably more abundant than H. spegazzinii falco or Aedes leucocelaenus, but, because of the small number of cases of yellow fever despite the considerate number of nonimmune persons exposed in the recent outbreak, it is suggested that these two last mentioned species may be the ones involved in the transmission of the disease to man in this area. As all of these species virtually disappear as adults during the dry season the question remains open as to how the virus is maintained during this unfavorable time of year. Two other species of Haemagogus taken in the study area, H. chalcospilans and H. argyromeris, were present in some abundance in the open or light second growth situations, but did not invade the forest to bite, and seem to be disqualified as vectors by the nature of their habits. The only other species which the evidence seems to render suspect is Sabethes chloropterus. This species demonstrates in its habits many of the characteristics of Haemagogus, is present in significant numbers, and seems better able to carry through the unfavorable dry season. There is, however, no direct evidence as to the ability of this species to transmit the yellow fever virus.
Departamento de Salud Publica, Republica de Panama and The Gorgas Memorial Laboratory, Panama, R. de P.