This paper presents the results of out door catches of Culicidae mosquitoes performed in the Ribeira Valley, State of S. Paulo, Brazil, where an outbreak of encephalits occurred in 1976 and 1977. These entomological investigations were made using several techniques for collecting mosquitoes, including human bait. Several places were chosen considering the environmental aspects related to human activities. In regions where high agricultural activities predominate and the primary forest was reduced to remaining spots, large numbers of Aedes serratus, Aedes scapularis and Culex (Melanoconion) sp. were caught. These mosquitoes were scarcely found in primary forest regions where no human cases of encephalitis occurred. These aspects suggest their participation in virus transmission. Beside this, other species, mainly Limatus and Psorophora, may possibly act as vectors, although with less epidemiological significance. It was noted that the scarcity of Aedes in the forest of the "Serra do Mar" system may be a cyclic phenomenon, as was pointed out in other investigations. This circunstance may explain the apparent barrier role to the epidemic that this mountain system seems to fulfill.
Culex; Arboviruses; Encephalitis, epidemic; Ecology; Aedes serratus; Aedes scapularis; Culex (Melanoconion) sp