Natural population dynamics of phlebotomine sandflies in Panama.

Abstract

The population dynamics of phlebotomine sandflics were studied in a Panamanian forest for 69 consecutive weeks. Sandfly populations were characterized by high species diversity, spatial heterogeneity and temporal change. Thirtyseven species were identified among 60,455 specimens collected. Light traps set near the ground captured 38.7% of the flies collected, 12.5% were caught in arboreal light traps, and 48.8% were aspirated from resting sites on tree trunks and buttresses. Anthropophilic species comprised 31.2% of all specimens, with light traps attracting nearly 2× as manynear the ground as compared to the forest canopy. Collecting stations in 3 distinct biotopes showed identical species composition but marked quantitative differences. Mature forest was a more productive sandfly habitat than secondary forest and, within mature forest, hilltop biotope was more productive than lowland (stream bed). Sandflies were perennial with marked seasonal fluctuations. Temporal density changes were related to amount and distributional pattern of rainfall which apparently acted by modifying the developmental conditions in the ground. Dryness or waterlogging of the forest floor, caused by scanty or excessive rainfall, was correlated with reduced adult density. Peak activity was attained during the first week of August with a second peak during the first half of January. The maximum increase, over the low level in dry season, was about 5-fold for the general population and 8-fold for the anthropophilic species. Seasonal population changes for a number of principal and anthropophilic species are presented.