Cytotaxonomy of four species in the Simulium perflavum species group (Diptera : Simuliidae) from Brazilian Amazonia

Polytene chromosomes of four members of the Simulium perflavum species grou p in Brazil are described, and a standard map for the species group is pres ented. Simulium rorotaense Floch & Abonnenc, S. perflavum Roubaud and an un described species (S. 'X') are chromosomally conservative, each representin g a single species with a unique preimaginal habitat. Chromosomal, morpholo gical and ecological evidence indicates that S. maroniense Floch & Abonnenc , previously considered synonymous with S. rorotaense, is a good species. I ndependent morphological and chromosomal analyses yielded 99.4% agreement i n separating larvae of S. rorotaense and S. maroniense. The two species can be distinguished by gill morphology or by a subterminal inversion on the l ong arm of chromosome III. Simulium maroniense consists of at least four cy totypes, each with different sex chromosomes and autosomal polymorphism pro files and associated with a particular landscape type, altitude, temperatur e regime or geographical location. Simulium rorotaense and S. maroniense sh are one unique inversion, as do S. perflavum and S. 'X', indicating two pai rs of sister species. The anthropogenic S. perflavum probably dispersed int o Central Amazonia sometime after the mid-1970s.