Phenology of an Established Population ofGalerucella calmariensis(L.) andG. pusilla(Duft.) (Coleoptera: Chrysomelidae) on Purple Loosestrife,Lythrum salicariaL. (Lythraceae), in Southwest Virginia

Two beetlesGalerucella calmariensisandG. pusilla(Coleoptera: Chrysomelidae) were introduced into Virginia for biological control of purple loosestrife (Lythrum salicaria). From initial releases of each species made in 1992 in Coeburn, Virginia, the beetles have been recovered for 3 consecutive years and are well established at the release site. Dispersal, as measured by the area covered by the beetles, has been slow; the area withGalerucellaspp. increased from 92 m2in 1993 to 414 m2in 1995. The proportion of purple loosestrife plants with one or more life stages of the beetles increased from 43% in 1993 to 67% in 1995. Both beetle species have one generation per year. Overwintering adults and eggs are found in early May, followed by larvae in late May through mid June. The F1adults emerge and feed briefly in late June and early July before going into diapause.