PLANT LICE
early part of the season the individuals of this species are round particularly on the under surfaces of the apple leaves. They cause the infested leaves to curl and to become distorted in a characteristic manner (Fig. 96). The stem mothers (Fig. 97 A, B) begin giving birth to young (C) about twenty-four hours after reaching maturity, and any one of the mothers, during the course of her life of from ten to thirty days, may produce an average family of fifty or more daughters, for all her offspring are females, too. When these daughters grow up, however, none of them is exactly like their mother. They all have one more segment in each antenna; most of them are wingless (D), but many of them have wings—some, mere padlike stumps, but others well developed organs capable of flight (Fig. 97 E).
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Fig. 96. Leaves of apple infested and distorted by the green apple aphis on under surfaces
Both the wingless and the winged individuals of this second generation are also parthenogenetic, and they give birth to a third generation like themselves, including wing- less, half-winged, and fully-winged forms, but with a greater proportion of the last. From now on there follows a large number of such generations continuing through the season. The winged forms fly from one tree to another, or to a distant orchard, and round new colonies. In
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