【Abstract】 Objective To improve the traditional preparation of the polytene chromosomes of blackflies and observe chromosomes abstracted. Methods Mature larvae of blackflies were selected, dissected and shelled out salivary glands. The traditional method was improved, and the clear polytene chromosomes slices were prepared after the use of new staining fluid, flush fluid and cleaning fluid. Results The improved method made chromosomes clearly and wholly in microscope. Conclusion The improved technique succeeded in the preparation of chromosome specimens of blackfly salivary gland, which was convenient for the observation of chromosomes shape and chromosomes variation in the laboratory.

In present paper,the checklist of blackflies in Hainan Island,China,was listed to December 2001,with 19 species.All species belong to 4 subgenera of Genus Simulium: Gophostilbia(8 species), Morops(1 species), Nevermannia(2 species) and Simulium(8 species).At the same time,a new species, Simulium( Gophostilbia) longitruncum sp.nov.,is described and illustrated.The type specimens are deposited in the Department of Biology Guiyang Medical College.