Adult beetles enter structures during the autumn but may be most troublesome during the spring when they become active after hibernation in attempting to get back outside to elm trees. Although these beetles do not harm humans or their possessions, they are sometimes confused with carpet beetles and other household pests and considered a nuisance by their presence. Beetles vary from yellow when young to olive green when mature, with a black stripe along the outer edge of the wing covers. There are four black spots on the thorax. During the winter, many beetles fade in color and by spring appear dull to olive green with the edge stripes less distinct.
Eyes are black and the antennae and legs are yellowish.
Elm Leaf Beetle. Life Cycle and Habits Elm leaf beetles overwinter as adults in homes, buildings, wood piles, tree bark crevices, debris at the tree base and other protected places. Egg-laying begins in late May and early June, with each female laying between 400 and 800 eggs over her life span. Eggs hatch in about seven days. Small, black larvae feed on the leaves and mature in two to three weeks.