HOST-PLANT RELATIONSHIPS OF APHIS-GOSSYPII GLOVER (HEMIPTERA, APHIDIDAE) IN AUSTRALIA

Aphis gossypii Glover is morphologically variable and polyphagous, and is a vector of many plant viruses. We investigated the ability of A. gossypii from different host plants and geographical areas within Aust ralia to colonise a,range of host plants in the laboratory. Samples di ffered in their success rates on particular laboratory hosts, but ther e was no absolute host specificity. Colonisation was significantly mor e likely if the previous host was of the same species, but hosts of th e same plant family were not equally suitable. The success rate of col onisation increased when aphids were repeatedly transferred to plants of the same species, suggesting that conditioning was occurring. When aphids were placed on ''poor'' hosts, such as broad bean, or on stress ed plants, they gave birth to offspring which developed into very smal l ''yellow dwarf'' adults. While some populations showed variant allel es, allozyme electrophoresis did not group aphids from different geogr aphic or host plant sources, nor indicate the presence of sibling spec ies.