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 (Hausmann), is polymorphic; despite the fact that in Australia its life cycle 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 throughout the year. the alate aphids are the offspring of apterous virginoparae and they occur first in November and then from late January to late April. Alate aphids appearing in early November produce only virginoparae, alates appearing from late November to late January produce 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. Although males and oviparae of this aphid appear seasonally, perpetuation of the species appears to be entirely parthenogenetic, and overwintering is accomplished in the form of cold‐hardy apterous virginoparae. Apterous virginoparae attain a rapid rate of nymphal development, large adult size, high fecundity and high population growth rate in the spring compared to summer, autumn and winter. However, populations peak in February‐March each year.