Hemlock Woolly Adelgid Life Cycle in North America
Hemlock woolly adelgids are all female in northeastern North America. They develop parthenogenetically (asexually) and have six stages of development: egg, four nymphal instars and adult. There are two overlapping generations per year. The overwintering generation (or sistens) is present from early summer through mid spring, and the spring generation (or progrediens) is present from early spring through mid summer.