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Samples of the neotropical malaria vector Anopheles darlingi from Bolivia, Brazil, and Venezuela were analyzed to test for differences in mitochondrial haplotype frequencies. With the use of molecular variance components and F-statistics, significant genetic variability of An. darlingi was found apportioned primarily among populations within regions or within populations, with regions defined either as biomes (n = 5) or ecoregions (n = 2). The Mantel analysis resulted in a significant correlation [Prob (r) = 0.009] between genetic and geographic distances, evidence that these populations are genetically isolated by distance. Such isolation could reflect differences in phenotypes for factors affecting vector capacity.

Three populations of Anopheles darlingi were studied for cuticular hydrocarbons, isoenzymes and patterns of peak biting activity. Differences were found in specimens from Costa Marques, a malaria endemic area; Dourado, a site with a very exophilic population and Juturnaíba, located near the type locality. Twelve hour collections from sunset to sunrise showed that An. darlingi from Costa Marques had a bimodal biting activity profile with a major peak at sunset and a minor peak at sunrise. At Dourado, the pattern was trimodal, with peaks at both morning and evening periods of twilight and near midnight. The Juturnaíba population showed a slight increase in activity near 2000 and 0100 h. Nei's genetic distances, determined by isoenzyme electrophoresis between pairs of populations, were low (D < or = 0.049). Using discriminant analysis for the cuticular hydrocarbons, 92.4% of the specimens from Costa Marques, 91.2% of the specimens from Dourado and 61.3% from Juturnaíba were correctly identified. Cuticular hydrocarbon and isoenzyme results matched very well: the smaller the Nei's distance, the more misidentifications occurred in the jackknife estimator used in the cuticular hydrocarbon analysis. This is the first report of cuticular hydrocarbon analysis in combination with isoenzymes to investigate neotropical anopheline species.