Fortnightly 25-hour catches, with human bait, were carried out in a modified environment of the "Jacaré-Pepira" River, Dourado County, S. Paulo, Brazil which is the original region of the "Araraquara" strain of Anopheles darlingi. The exophylic biting activity was mostly nocturnal with bimodal rhythm, showing two clear peaks corresponding, respectively, to dusk and dawn. Going into crepuscular details two secondary peaks were observed, an eocrepuscular preceding the intracrepuscular one As, by means of chromosome arrangement studies, this population was found to have low polymorphism, it is supposed that those rhythms are, in a good measure, of endogenous command. The number of mosquitoes biting increased during the hot, wet season and decreased remarkably during the dry, cold one. There was some evidence that An albitarsis may also show a bimodality in its nocturnal biting activity rhythm.
Anopheles darlingi; Malaria; Anopheles albitarsis; Mosquitoes; Ecology