Electrophoresis of isozymes was carried out to determine the degree of genetic variability in arrhenotokous and thelytokous forms of Mesochorus nigripes. Although the over-all heterozygosity (H-a) for 12 loci in 10 enzyme systems was 0.187 for the arrhenotokous form and 0.103 for the thelytokous form, a paired comparison t-test showed no significant difference. Nei's coefficient of genetic identity between these 2 forms I = 0.982. none