The two leaf-beetles Galerucella calmariensis and G. pusilla share similar ecology and life history. Adults overwinter in the leaf litter and emerge in early spring synchronized with host plant phenology. Adults feed on young plant tissue causing a characteristic "shothole" defoliation pattern. Females lay eggs in batches of two to ten on leaves and stems from May to July. First, instar larvae feed concealed within leaf or flower buds; later instars feed openly on all aboveground plant parts. Larval feeding strips the photosynthetic tissue off individual leaves creating a "window-pane" effect by leaving the upper epidermis intact. Mature larvae pupate in the litter beneath the host plant. At high densities (greater than 2-3 larvae per centimeter of shoot), entire purple loosestrife populations can be defoliated. Adults are mobile and possess good host finding abilities. They spread several miles from their original release sites in a few years. Peak dispersal of overwintered beetles occurs during the first few weeks of spring. New generation beetles have dispersal flights shortly after emergence and are able to locate patches of host plants as far away as one kilometer.
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Left to right: Galerucella eggs, larvae and damage to purple loosestrife.