They may be resting in the mulch at the base of the plants in the day or on leaves of large trees. Inspect your plants in late evening or at night if you suspect these beetles. Adult emerges from pupa case in late summer but remains in the soil 6 to 8 inches deep until the next spring. The elm leaf beetle is found in all sections of the country where elms are used as shade trees. This tree is apparently the only host plant for this insect.
Mature larvae are about of an inch long and yellow green with two black strips down the back.
The adults eat small, roughly circular holes in the leaves. The larvae usually skeletonize the leaf from the underside. When ready to pupate, they congregate in large numbers on the trunk or at the base of the tree. It flies to elms in May or June. Each female may lay 400 to 800 eggs.