Fundatrix
Guides
Hormaphis
witch hazel aphids, palm aphids
Hormaphis is a genus of gall-forming aphids in the family Aphididae, containing at least three described species distributed mainly in eastern North America. The genus includes the witch hazel cone gall aphid (H. hamamelidis), which induces distinctive cone-shaped galls on witch hazel (Hamamelis virginiana). Species in this genus exhibit complex host plant manipulation, including alteration of host phenolic metabolism to create favorable gall environments. The life cycle involves a bet-hedging strategy where eggs hatch before host budbreak to ensure gall formation opportunities.
Hormaphis hamamelidis
Witch-hazel Cone Gall Aphid
Hormaphis hamamelidis is a gall-forming aphid that induces distinctive red, cone-shaped galls on witch-hazel (Hamamelis virginiana) leaves. The species exhibits host alternation, with sexual reproduction and gall formation on witch-hazel in spring, followed by migration to birch (Betula) for parthenogenetic summer generations, and return migration to witch-hazel in autumn. Founding females (fundatrices) actively manipulate host plant phenolic metabolism, increasing condensed tannins and decreasing hydrolyzable tannins within galls to enhance their own reproductive success. Gall size, determined largely by fundatrix manipulation of plant growth, is the primary predictor of fundatrix fecundity rather than leaf position or plant vigor per se.
Phylloxera conica
hickory phylloxeran, hickory phylloxera
Phylloxera conica is a gall-forming insect closely related to aphids that induces distinctive globular galls on hickory leaves and petioles. The insect overwinters as eggs on bark or near old galls, with nymphs emerging during bud break to feed on new growth. Their feeding stimulates abnormal plant cell development, creating hollow galls that provide shelter and food. The species has a complex life cycle involving multiple generations, with winged forms eventually dispersing to lay overwintering eggs. Heavy infestations can reduce tree vigor and nut production in hickory trees.
Phylloxera crypta
Phylloxera crypta is a gall-forming insect closely related to aphids, known to induce distinctive galls on hickory trees (Carya species). Like other phylloxerans, this species manipulates plant tissue development through chemical secretions during feeding, creating protective structures that house developing nymphs. The species exhibits a complex life cycle involving multiple generations and both sexual and parthenogenetic reproduction phases.