Key words: Aedes aegypti -chitin synthesis inhibitors -temephos -deltamethrin -novaluron -cross-resistance Among the arboviruses transmitted by mosquitoes throughout the world, dengue is presently the most relevant; it is endemic to all of the continents, except Europe (Nogueira et al. 2001, Forattini 2002, Claro et al. 2004. Brazil has an alarming dengue incidence with several outbreaks all over the country and an increasing incidence of severe cases. Therefore, major public health campaigns target this disease (Teixeira et al. 1999, Câ-mara et al. 2007, MS/SVS 2009.Specific drugs and an effective vaccine against dengue virus are not yet available (Durbin & Whitehead 2010). Consequently, the only way to control the dengue epidemiological network is to target the virus' vector, Aedes aegypti (Medronho 2006. Although the elimination of potential Aedes breeding sites is increasingly considered a crucial component of dengue control, the utilisation of chemical insecticides is still a common measure. Until very recently, the most commonly used insecticides against Aedes in Brazil were the organophosphate temephos and the pyrethroid deltamethrin, which are used to control the larval and adult populations, respectively .The continuous use of chemical insecticides can lead to the dissemination of resistance and the consequent failure of the control efforts. Therefore, alternative methods of controlling disease-transmitting vectors are urgently needed. Two examples are entomopathogenic bacteria and insect growth regulators (IGRs). The biological insecticide Bacillus thuringiensis serovar israelensis (Bti) has been employed against Ae. aegypti in various municipalities of Brazil. However, the reduced field persistence of commercially available Bti formulations is an obstacle; under tropical conditions, the maximal residual effect observed lasted four weeks .In contrast to the classical chemical insecticides and biolarvicides, IGRs are not directly toxic, but act selectively on the development, metamorphosis or reproduction of the target insect species (Hoffmann & Lorenz 1998, Martins & Silva 2004. Among IGRs, the chitin synthesis inhibitors (CSIs) act by interfering with the synthesis or deposition of chitin on the exoskeleton or other chitinised internal structures, such as the peritrophic matrix (Merzendorf & Zimoch 2003, Merzendorf 2005.Novaluron is a CSI that is already utilised in agriculture. It is highly effective against Coleoptera, Homoptera and Lepidoptera larvae of several crop pests . It can act through ingestion, as verified in the larvae of the moth species Spodoptera littoralis and Helicoverpa armigera, or through contact, as reported with the flies Bemisia tabaci and Trialeurodes vaporariorum (Ishaaya et al. 1996(Ishaaya et al. , 1998. Novaluron is also efficient against Ae. aegypti larvae, as reported by Mulla et al. (2003) and Arredondo-jiménez and Valdez-Delgado (2006). Because novaluron is recommended by the World Health Organization for use in drinking water, it represents a potential tool in the con...

BackgroundComplexes of cryptic species are common in several taxa and this is also the case in the Anopheles genus, a group including all known human malaria vectors. The Anopheles albitarsis complex comprises at least nine cryptic species, some of which are implicated as vectors of human malaria. Several different types of data have been generated for this species complex such as cytogenetics, alloenzymes, morphological and feeding behavioral, hybridization experiments, RAPD-PCR and RFLP and mitochondrial and nuclear markers. Studies focused on its postzygotic isolation are still somewhat rare in the literature despite their importance to understand the speciation process and the level of gene flow potentially occurring among the different sibling species.MethodsHybridization experiments between Anopheles albitarsis s.s. and Anopheles marajoara, as well as backcrosses between hybrids and Anopheles albitarsis s.s., were performed using the induced mating technique. Results were compared to intraspecific crosses. Larva-to-adult viability and sex ratio were also assessed.ResultsMale hybrids show very low insemination rates and nearly complete sterility, apparently due to abnormalities in their reproductive organs. Evidence of partial sterility among the hybrid females was also observed.ConclusionsOur data indicated that Anopheles albitarsis s.s. and Anopheles marajoara show a high level of postzygotic isolation with a strong hybrid male sterility. This result is consistent with the Haldane’s rule which states that in interspecific crosses the heterogametic sex is the first to be affected. However, the fact that the females are not completely sterile raises the possibility of introgression between these two siblings species.

Background: Complexes of cryptic species are common in several taxa and this is also the case in the Anopheles genus, a group including all known human malaria vectors. The Anopheles albitarsis complex comprises at least nine cryptic species, some of which are implicated as vectors of human malaria. Several different types of data have been generated for this species complex such as cytogenetics, alloenzymes, morphological and feeding behavioral, hybridization experiments, RAPD-PCR and RFLP and mitochondrial and nuclear markers. Studies focused on its postzygotic isolation are still somewhat rare in the literature despite their importance to understand the speciation process and the level of gene flow potentially occurring among the different sibling species. Methods: Hybridization experiments between Anopheles albitarsis s.s. and Anopheles marajoara, as well as backcrosses between hybrids and Anopheles albitarsis s.s., were performed using the induced mating technique. Results were compared to intraspecific crosses. Larva-to-adult viability and sex ratio were also assessed.