We investigated the NOR distribution in ten populations of Physalaemus cuvieri from different regions of Brazil and Argentina. A high variability in NOR pattern was observed and provided a useful tool in grouping several populations. The specimens from the state of Tocantins, northern Brazil, could easily be distinguished from all the other analyzed populations, since its karyotype presented NORs in the chromosome pairs 1,3,4 and 10 (and sometimes also in chromosome 5), and several pericentromeric C-bands. A NOR-site in chromosome 9 characterized three populations from the northeastern region of Brazil. Interestingly, the P. cuvieri populations located in opposite extremes of the geographic distribution had, as a fixed condition, the presence of NORs in 8q int and llp. Besides interpopulational divergences, intrapopulational variability was observed in the number of NORs, except for populations from the states of Bahia and Minas Gerais, which are boundary states respectively in the northeastern and southeastern regions of Brazil. In relation to NOR size, interindividual variations occurred in all Brazilian and Argentinean populations. Additionally, intraindividual variability in NOR size was detected in specimens from Minas Gerais. The data presented herein revealed substantial geographic polytypic variation in P. cuvieri and indicated that a taxonomic reexamination of this species is necessary.

Polytene chromosome preparations were obtained from larval, pupal and adult female Malpighian tubules of Aedes aegypti. The Malpighian tubules of the pupae (0-4 h old) from larvae reared at 20ºC provided the best cytogenetic analysis. The interaction of nucleic acids and proteins that influence the spreading of the chromosomes could be reduced with the preparation technique of the sheets submitted to a stronger treatment starting with the hypotony of tissue and successive bathings with acetic acid. A simple technique should facilitate molecular cytogenetics used in the location of resistance and vector competence genes.

Dipteran polytene chromosomes provide an excellent model for understanding in species complexes, as well as for structural and functional cytogenetics. The status of species in the Culex pipiens complex is controversial and the use of polytene chromosomes for cytogenetic analysis in the subfamily Culicinae has been difficult because of methodological problems. In this study, Malpighian tubule polytene chromosomes were obtained from young (0 to 12 h, 20ºC) and old (20 to 42 h, 28ºC) laboratory-bred C. pipiens quinquefasciatus pupae. The chromosome maps for this species were constructed and compared with published data for C. pipiens pipiens and C. p. quinquefasciatus. Although the banding patterns were conserved between subspecies, analysis of the structural variations in the bands and interbands revealed differences apparently related to the physiological stage and ecogeographical strain. The organization of the centromeric regions in larval and pupal chromosomes showed greater similarity to each other than did those of pupal and adult chromosomes. The use of pupal polytene chromosomes for in situ hybridization with vector competence probes is discussed.

Chromosomal studies were carried on six larval populations of Simulium (Chirostilbia) pertinax from different locations in Brazil. Larvae were collected in the states of Paraná, Rio Grande do Sul, Rio de Janeiro and São Paulo. Polytene chromosome map comparisons within and among populations showed no differences in banding pattern, except for some limited polymorphism (secondary NOR and four band polymorphisms). There were no chromosomal variations associated with the resistance or susceptibility of the larvae to temephos. The chromosomal homosequentiality found among the six populations suggests that S. pertinax may be a monomorphic species.