THE EGGS AND LARVAE OF PACHYBRACHIS PECCANS AND P. BIVITTATUS, WITH A KEY TO THE KNOWN IMMATURE STAGES OF THE NEARCTIC GENERA OF CRYPTOCEPHALINAE (COLEOPTERA: CHRYSOMELIDAE)

Abstract

AbstractThe egg and larval instars of Pachybrachis peccans Suffrian and P. bivittatus Say are described and illustrated. Adults of both species appear in late May, feed on willow leaves, mate and oviposit in June–July. The larvae, unable to climb the host plants, feed in the leaf litter of dead leaves of willow; they reach the second-last or last instar by the end of the fall; then they seal their case and overwinter. Pupation occurs the following spring, probably in early May.Larval instars can be distinguished as follows: first instar with egg bursters on meso- and metathorax, with typical head chaetotaxy consisting of flattened-papillate setae and 1 pair of very long simple setae, and tibiae with 2 pairs of spiniform setae; older instars without egg bursters, and showing differences in size, in head and pronotal chaetotaxy, and in the number of spiniform setae on the tibiae.In the larvae, the premental sclerites of the head seem to be present throughout the Campsomata, a group with case-bearing larvae and not only in the Lamprosomatinae as previously reported.