Natural Breeding Places for Phlebotomine Sand Flies (Diptera: Psychodidae) in a Semiarid Region of Bahia State, Brazil

Few microhabitats have been previously identified as natural breeding places for phlebotomine sand flies so far, and little is known about the influence of climate variables in their density. The present study was conducted in a dry region with a semiarid climate, where visceral leishmaniasis occurs in humans and dogs. The occurrence of breeding places in specific microhabitats was investigated in soil samples collected from five houses, which were also the location used for sampling of adults. All the microhabitats sampled by our study were identified as natural breeding places due to the occurrence of immature forms of sand flies. On a weekly basis, the number of adult sand flies captured was positively correlated with the mean temperature from preceding weeks. These results, in addition to promoting an advance in the knowledge of sand flies biology, may furnish a tool for optimizing the control of the sand flies, by indicating the most suitable periods and microhabitats for the application of insecticides. 1. Introduction Despite the medical importance of leishmaniasis, little is known about the natural breeding places of its vectors. Most previous attempts to identify the preferred microhabitats for the oviposition of sand flies in the Neotropical region have produced disappointing yields, resulting in a small number of positive soil samples and immature forms [1–4]. Some recent studies (e.g., Alencar [5] and Singh [6]), however, have successfully obtained high amounts of immature forms due to the sampling of suitable places for larval development. As observed by Newstead [7], the immature forms of sand flies are more concentrated in microhabitats that exhibited specific conditions, as the presence of organic matter, humidity, and low levels of light. Studies conducted in rain forests (e.g., Hanson [8], Alencar et al. [5]) corroborate these observations, as shown by the greater numbers of immature forms found in soil with litter, between roots and under fallen trunks. Similar edaphic conditions, although in different microhabitats such as soil cracks, have also been observed in studies conducted at regions with dry climates (e.g., Deane and M. P. Deane [9], Ferreira et al. [1]), to be more likely to find immature forms of sand flies. Dry climate regions experience more pronounced climatic variations than regions with humid climates typical of rain forests, so the density of vectors may exhibit different characteristics as well. Studies conducted in rain forest regions (e.g., Hanson [8], Dias-Lima et al. [10]) observed high densities of vectors