Abstract
Clones of Myzus persicae were identified by the body colour and esterase differences, and its field populations on various host plants were analyzed into forms. One hundred and fifty-three clones were sampled from the field populations on peach, cabbage, radish, spinach, potato, tobacco, etc. at 3 localities in Japan and electrophoretically examined for their esterase activity at 5 polymorphic esterase loci. A total of 28 forms with different combinations in the body colour and esterase pattern were actually detected. From the overwintering populations at 3 sites in Kyoto 10 different colour-esterase forms were detected.The red forms detected on potato and tobacco within the same area were completely different from each other in their esterase patterns. One particular form was found with high frequency on a wide range of hosts, excluding at least tobacco, at all localities surveyed (form-16). This form appears to be able to reproduce during the midsummer and persist through the severe winter even under the snow.
