Polytene chromosomes of Simulium (Wilhelmia) xingyiense (Diptera: Simuliidae) from China.

A standard photographic map of Simulium (Wilhelmia) xingyiense Chen and Zhang was constructed from larval salivary gland polytene chromosomes and is described herein. Polytene chromosomes from wild larvae collected from three populations in Guiyang,Guizhou Province,China were analyzed. By using an upgraded method of preparation,the polytene chromosomes of the larval salivary glands of S. (W.) xingyiense were observed and analysed. The results indicated that this species has three pairs of chromosomes (2n = 6) which are arranged from the longest to the shortest. Chromosome Ⅰ is metacentric while the chromosome Ⅱ and III are submetacentric. The nucleolar organizer is situated near the centromeric band of the short arm of chromosome Ⅰ. The Balbiani ring and double bubble are located about the middle of short arm of chromosome Ⅱ. The pericentric heterochromatin of all chromosome arms forms an evident chromocenter. High inversion polymorphism is observed,with 0. 64 inversions per individual. Thus,the polytene chromosomes of S. (W.) xingyiense are species-specific. Inversion is one of the characteristics of polytene chromosomes of S. (W.) xingyiense.