EFFECTS OF LEAF AGE ON OVIPOSITION AND ON OFFSPRING FITNESS IN THE IMPORTED WILLOW LEAF BEETLE PLAGIODERA-VERSICOLORA (COLEOPTERA, CHRYSOMELIDAE)

Imported willow leaf beetles Plagiodera versicolora oviposit on willow leaves, and both larvae and adults feed on the leaves, In the field, eggs were found on leaves near the center of branchlets, and the numbe r of eggs per cluster was independent of the leaf area and position. H owever, in the laboratory, females chose young leaves over old leaves, for both oviposition and feeding and choice did nor rely on informati on on relative position or size of leaves. Developing on young versus old leaves may provide both advantages and disadvantages. In the labor atory, lan ae developed more quickly and attained a greater adult weig ht when fed young versus old leaves, perhaps because of increased mand ibular wear of larvae fed old leaves. However, in the field, survival of eggs was lower on young versus old leaves. In the laboratory, rates of cannibalism and survivorship to adulthood did not differ on young versus old leaves.