The characteristic features of the salivary gland chromosomes of D. nasuta collected from Seychelles were described. The banding patterns of four long arms of this species somewhat differ from those of the Indian nasuta which is closely related species to the Seychelles nasuta.
Chromosomal polymorphisms of this species in five populations, Sri Lanka, Seychelles Kenya, Madagascar and Mauritius, were investigated. 6 heterozygous inversions of the X chromosome, 7 of 2L chromosome, 3 of 2R chromosome and 14 of 3 chromosome were found in each arm. The most of inversions showed very low frequency, while 4 inversions of 3-C, 3-F, 3-G and 3-J were found abundantly in Seychelles. More than 80％ individuals showed these four inversions simultaneously or independently. It was known that individuals which had these inversions were always at advantage and a rigid polymorphism concerning these four inversions is established in the Seychelles nasuta population.