Abstract: Numerical taxonomy studies for intraspecies differentiation of cotton aphids wer e carried out with the measurement of fourteen morphological characters of the c otton aphids on four summer host plants,during two growth stages of cotton and u nder three temperatures in laboratory respectively.The results of cluster and Go wer distance analyses showed that among four summer hosts,there wer e no differences either between seedling aphids with the green and yellow color or dwarf aphids with the five segment and six segment antenna.But the populatio n differentiation were significant between the aphids on cotton seedling and on potato and between the aphids on cotton seedling and the dwarf aphids(summer aphids).The laboratory populations under 30℃ or the yellow color seedling aphi ds tended to be analogous with dwarf aphids.Seven main morphological characters were analyzed for differentiating such intraspecies populations.

Key words: Aphis gossypii Glover, cluster analysis, Gower distance, morphological characters, Aphis gossypii Glover, cluster analysis, Gower distance, morphological characte rs