Life History of Natural Populations of the Imported Willow Leaf Beetle, Plagiodera versicolora (Coleoptera: Chrysomelidae)

Two populations of the imported willow leaf beetle, Plagiodera versicolora (Laicharting), in northern Illinois were studied during four spring seasons between 1979 and 1983. The life cycle includes an egg stage of 5–6 days, a larval stage of 14 days, a pupal stage of 4–5 days, and an adult stage lasting 3–4 weeks. Mean clutch size in the field ranged from 15 to 19 eggs for the four seasons; mean size of eclosing larval groups ranged from 8 to 13. Larvae remain aggregated during the first three stadia, and there is a positive effect of initial group size on larval survivorship