SEASONAL OCCURRENCE, DEVELOPMENT AND REPRODUCTIVE-BIOLOGY OF THE DIFFERENT MORPHS OF ERIOSOMA-LANIGERUM (HAUSMANN) (HEMIPTERA, APHIDIDAE) IN THE NORTHERN TABLELANDS OF NEW-SOUTH-WALES

As with many other aphids, the woolly aphid, Eriosoma lanigerum (Hausm ann), is polymorphic; despite the fact that in Australia its life cycl e is restricted to apple trees. The different morphs are: (1) apterous virginoparae; (2) alate sexuparae or virginoparae; and (3) sexuales ( males and oviparae). The apterous virginoparae occur on apple trees th roughout the year. The alate aphids are the offspring of apterous virg inoparae and they occur first in November and then from late January t o late April. Alate aphids appearing in early November produce only vi rginoparae, alates appearing from late November to late January produc e a mixture of virginoparae and sexuales whereas those appearing from February to April produce exclusively sexuales. Sexuales are apterous; have degenerate mouth parts and oviparae produce non-viable eggs. Alt hough males and oviparae of this aphid appear seasonally, perpetuation of the species appears to be entirely parthenogenetic, and overwinter ing is accomplished in the form of cold-hardy apterous virginoparae. A pterous virginoparae attain a rapid rate of nymphal development, large adult size, high fecundity and high population growth rate in the spr ing compared to summer, autumn and winter. However, populations peak i n February-March each year.