Lutzomyia longipalpis s.l. (Diptera: Psychodidae) is the principal vector of Leishmania infantum chagasi in the Americas, and constitutes a complex of species. Various studies have suggested an incipient speciation process based on behavioral isolation driven by the chemotype of male sexual pheromones. It is well known that natural barriers, such as mountains and rivers can directly influence population divergence in several organisms, including insects. In this work we investigated the potential role played by the Sao Francisco River in eastern Brazil in defining the current distribution of Lu. longipalpis s.l. Our studies were based on analyses of polymorphisms of the cytochrome b gene (cyt b) sequences from Lu. longipalpis s.l. available in public databases, and from additional field-caught individuals. Altogether, 9 distinct populations and 89 haplotypes were represented in the analyses. Lu. longipalpis s.l. populations were grouped according to their distribution in regards to the 10°S parallel: north of 10°S (<10°S); and south of 10°S (>10°S). Our results suggest that although no polymorphisms were fixed, moderate genetic divergences were observed between the groups analyzed (i.e., F ST = 0.184; and Nm = 2.22), and were mostly driven by genetic drift. The population divergence time estimated between the sand fly groups was about 0.45 million years (MY), coinciding with the time of the change in the course of the Sao Francisco River, during the Mindel glaciation. Overall, the polymorphisms on the cyt b haplotypes and the current speciation process detected in Lu. longipalpis s.l. with regards to the distribution of male sexual pheromones suggest a role of the Sao Francisco River as a significant geographical barrier in this process.

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(Galvão et al. 2003, Galvão & Angulo 2006, Costa et al. 2006, Costa & Felix 2007, Sandoval et al. 2007, Bérenger & Blanchet 2007, Martinez et al. 2007) and is a vector of Trypanosoma cruzi. Its geographical distribution is limited to the Brazilian states of Bahia, Espírito Santo, Minas Gerais (MG), and Rio de Janeiro (Galvão et al. 2003). Although considered to be of secondary importance in T. cruzi transmission to man, this species shows high rates of trypanosome infection (Santos et al. 1969a,c, Pinto et al. 1969, Barros et al. 1975, Sessa & Carias 1986, Dias et al. 1989, Gonçalves et al. 1998, Santos et al. 2005 and is often captured in man-made habitats, with frequent reports of adult bugs invading houses (Santos et al. 1969b, Ferreira et al. 1986, Sessa & Carias 1986, Dias et al. 1989, Gonçalves et al. 1998, possibly attracted by light (Ferreira et al. 1986 to T. cruzi are very high, especially in adult bugs captured indoors in Itahomi. However, Chagas disease is rare in the area, a prevalence of only 0.4% has been recorded as part of a national serological survey (Camargo et al. 1984). It is not known whether the low transmission of T. cruzi to man is due to characteristics of the vector (the long interval between feeding and defecation) or the strain of parasite involved.Among the available taxonomic marker techniques, morphometry of the head, random amplified polymorphism of DNA (RAPD) and isoenzyme analysis have been most used in triatomine population studies (Costa et al. 1997, Dujardin et al. 1998, Borges et al. 2000, Soares et al. 2001, Barbosa et al 2003. We used these three techniques to investigate T. vitticeps population dynamics in the Itanhomi district. MATERIALS AND METHODSStudy area -Itanhomi (19°11'15"S, 41°48'45"W) has an estimated population of 11,012 inhabitants. The urban and rural area comprise 93 localities. In 11 of the rural sites (Adão Daniel, Cabeceira do Guido, Francisco Inácio, Jesus Julião, Jose Horta, Jose Noberto, João Caboclo, Júlio Carlos, Liés Alves, Orides I, and Valico) the search for T. vitticeps was intensively performed in 2002 in domestic and peridomestic environments. The following year, sylvatic sampling was attempted in Cabeceira do Guido, particularly in a wooded area 100 m from a house where adult triatomines are periodically detected.Houses in Itanhomi in which T. vitticeps was sampled conform to a distinct pattern of construction, being built on stilts.The floors of these dwellings are wooden 15 Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 103(1), February 2008 and often have cracks that allow triatomines to pass in and out; the floor is a kind of roof for the open basement (classified as the peridomicile). Houses are built on stilt, providing shelter for domestic animals and storage of materials. Furthermore, 100-500 m from the houses there are remnants of Atlantic forest and rocks, constituting sylvatic habitat for the bugs. This peculiar characteristic of the locality is the proximity of the habitats.Insects -A pool of T. vitticeps captured in Itanhomi ...

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In a study of the phlebotomine sandflies (Diptera: Psychodidae) in a forest reserve in Recife, Pernambuco state, north-eastern Brazil, the sandflies landing on human bait between 1.00 and 1.42 h after sunset were collected weekly for 2 years. Although 10,287 sandflies of 10 Lutzomyia species were collected, almost all (96.5%) of the sandflies caught were Lu. umbratilis. This species and several others caught are potential vectors of some of the Leishmania parasites that cause human disease. The recorded landing rate for Lu. umbratilis peaked, at the high level of 333.3 flies/person-hour, during the collections made in May 2003.The relative rarity in the collections of males of some of the species caught probably indicates that these species do not lek on their bloodmeal sources. It is likely that the sizes of the local populations of species that are not very anthrophilic, such as Lu. flaviscutellata, are much larger than indicated by the collections made on human bait.