Observations on mosquito activity in primitive highland rain forest in the Ribeira Valley, S. Paulo, Brazil

Abstract

With fortnightly rhythm, 25-hour catches of Culicidae mosquitoes were carried out, at ground level, with human bait, in a primitive rain forest in a highland relief area of the Ribeira Valley region, S. Paulo, Brazil. Besides this, regular simultaneous catches employing Shannon traps were made within and outside the forest environment. Results obtained are presented and discussed. An. cruzii proved a highly dominant species and An. bellator also showed ininterrupted daily activity, increasing at night. They showed too, a clear peak of biting activity during the dusk crepuscular period, sustaining their activity outside the forest environment. During the dawn crepuscular period these two species showed a peak too, and for both crepuscular periods the peaks were immediately followed by ether secondary ones, of lower intensity. The name paracrepuscular is suggested for this type of rhythm. Cx. sacchettae presented an essentially nocturnal pattern with eocrepuscular rhythm, while Ae. serratus and Ps. ferox presented a diurnal one, with some evidence of paracrepuscular activity. The epidemiological importance of An. cruzii for the transmission of infections, mainly malaria, and its role for the biogeographical characterization of this primitive ecossystem is emphasized.