Larvae are skeletonizers, meaning that they feed on the tissue
between the veins, but leave the veins intact. Adults chew holes
in the leaves. Adult beetles are dark shiny blue, and about 5 mm
long. The mature larvae are a little longer and narrower than the
adults, brown to black above and yellowish below.
Biology: One generation is reported per
year. Adults hibernate during the winter in duff at the base of
trees and in other sheltered places. They emerge in early spring
to resume feeding. Eggs are laid in clusters on foliage. Larvae
hatch and begin feeding within a few days. One source reports that
larvae mature in August; but in the Southwest they mature earlier
in the season.
Effects: No long-term effects are documented.
Outbreaks are generally short lived and sporadic with heavy defoliation.
Trees tend to recover quickly.
Similar Insects and Diseases: Although other
defoliators feed on alder, outbreaks of these other insects have
not been reported.