Witch-hazel Cone Gall Aphid

The first generation of the year is composed entirely of female fundatrices (also called stem mothers), which hatch from winter eggs laid on the bark of witch-hazel. Shortly following bud break, she begins to feed on leaf tissue. She then repeatedly “stings” the abaxial surface of the leaf to induce gall formation. A gall forms around her approximately 7–14 mm tall on the adaxial (upper) side of the leaf. She then reproduces around 45 female offspring through parthenogenesis. The second generation consists of alate sexuparae, which are winged females. As the second generation matures within the gall, the stem mother and juveniles feed on witch-hazel phloem and push waxy detritus through the gall opening on the leaf's underside. All the offspring from a given gall mature at the same time and become winged migrants. At maturity, the females leave the gall and begin to lay the eggs of the third generation on surrounding leaves, often on the same plant that they emerged from. The third generation comprises both male and female sexuales. Individuals begin mating after their final molt. Mating may occur on the leaves where the aphids hatched or on the plant's winter buds. There, females deposit between five and ten eggs, which remain throughout the winter.