About Stegophylla essigi Hille Ris Lambers, 1966
Stegophylla essigi, commonly called the California woolly oak aphid, is an aphid species native to North America. This species has been found feeding on a wide range of oak species in California, which includes blue oaks, valley oaks, Oregon white oaks, coast live oaks, interior live oaks, California black oaks, and scrub oaks. Woolly oak aphids pass the winter in the egg stage. They produce several generations within a single year. In spring, females of this species reproduce parthenogenically, meaning reproduction occurs without mating. In fall, both male and female aphids are produced. Adult males of this species can be either winged or wingless. For Stegophylla essigi specifically, oviparae, along with both winged and wingless males, are produced in November. Populations of Stegophylla essigi can continue reproducing parthenogenically on evergreen oak species like coast live oak, particularly in leaves that have been tied together by caterpillar silk. A clear visible indicator that California woolly oak aphids are present is upward-folded oak leaf margins that turn reddish.
