Neuroblast and salivary gland chromosomes were studied in Feulgen squash preparations of SIMULIUM VITTATUM larvae. The haploid complement consists of three metacentric chromosomes; the arm ratio of the longest (1) and shortest (3) is approximately as 1: 1, that of the second
as 1: 2. Centromere regions of salivary gland chromosomes are expressed as characteristic expanded drums with large disorganized chromomeres. The third salivary gland chromosome bears the single large nucleolus and a smaller granular structure comparable to the Ring of Balbiani of chironomids.
Pairing of the two constituents of salivary gland chromosomes is quite loose regardless of the degree of polyteny. Photographic maps are given of the standard band sequence of the entire complement. Relatively short inversions are the commonest type of structural rearrangement. From preliminary
observations on further black fly species and an eclectic treatment of the nematocerous literature, morphological characteristics of salivary gland chromosomes are discussed with respect to their value in delimiting taxonomic segregates and determining phylogenetic relationships.
Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.