Eastern hemlock is an important component of forests in the eastern U.S. Unfortunately, an invasive insect species, the hemlock woolly adelgid (Adelges tsugae) (native to Asia) (Hemiptera: Adelgidae), has caused tremendous decline of hemlocks in the northeastern U.S. In 2002, the hemlock woolly adelgid was first found in the Great Smoky Mountains National Park (GRSM), where it is now widely distributed. Little is known about this invasive insect species in the southeastern U.S. A two-year study to better define the biology and seasonality of the hemlock woolly adelgid in the GRSM was completed in 2006. This poster describes the life cycle of this invasive parthenogenic species and compares seasonality data in the GRSM with life history data from the northeastern United States. In general, the development of hemlock woolly adelgid in the GRSM was about two to four weeks earlier than that reported in similar studies in the northeastern U.S. Eggs were found from February to June, with egg densities peaking in late February/early March (sistens) and late May/mid June (progrediens). Crawlers, the most mobile state, were present from late March to late June; densities of crawlers were highest from late March to mid April and again in late June. A better understanding of the life cycle of hemlock woolly adelgid in the southeastern U.S. will enable scientists and land managers to enhance IPM programs against this problematic pest. Improvements in timing of chemical insecticide applications and/or releases of biological control agents will contribute to reductions of populations of hemlock woolly adelgid.