Abstract: The present paper deals with meiosis and chromosomes in 45 species of Chinese leafhoppers, among which 44 species are cytologically studied for the first time. Chromosome numbers vary from 2n=12 to 26, and sex determination is XO type in all species. Chromosomal histogram of Cicadelloidea shows that chromosome number vary from 2n=8 to 28, the predominant type is 2n=18(16+XO), and other types such as 2n=16, 20 and 22 are also very common. Positive trend on chromosome number evolution was not found, and 2n=22(20+XO) is suggested to be initial karyotype. Unequal exchange between homologous chromosomes induced by translocation is the main mechanism of karyotype evolution. Male meiosis indicates that the relationship between Cicadelloidea and Membracoidea is very close, and they share the following characteristics: ①volume of spermatocytes is bigger than that in Cercopoidea and Cicadoidea; ② chromosome behaviors during meiosis are similar; ③fewer chromosomes but with bigger volume; ④differing from Fulgoroidea, meiosis prophase Ⅰ has typical bouquet stage but without diffuse stage. It is suggested that Membracoidea, are more primitive than Cicadelloidea, since chromosome numbers are much varied in Cicadello Idea but conservative in Membracoidea.

Key words: Cicadelloidea, karyotype, chromosome, meiosis