Insect identification > Coleoptera > True Coleoptera > Elm leaf beetle

Elm leaf beetle

The elm leaf beetle (Galerucella xanthomeloena Schr.). - This European insect appears to have reached this country at Baltimore about 1834 and has now spread through most of the New England and Middle Atlantic states and westward to the Mississippi River, though not everywhere present within these limits. It is also found on the Pacific Coast.

The adult beetle is about a quarter of an inch long, dull yellow in color, with black spots on the head and pronotum, a black band near the outside of each elytron, and a short streak at the base of each, nearer the middle.

The beetles winter over in protected places and in the spring the dull yellow has changed to an olive green. They fly to the elm trees when the foliage develops and feed, eating irregular holes in the leaves and from time to time laying yellow eggs on the underside of the leaves, usually about 25 in number and nearly always in two rows, side by side.

The eggs hatch after about a week and the tiny yellow and black grubs feed for about 3 weeks, working on the under surface and leaving the upper epidermis of the leaf unbroken.
When full­grown and about half an inch long, they crawl down the tree to the trunk and pupate for from 1 to over 3 weeks according to the temperature, either in crevices of the bark on the lower part of the trunk or on the ground near the foot of the tree.

In the more northerly states the larvae feed during June. Farther south they begin in May and a second generation feeds during the late summer or early fall. The European elms are most severely injured by this insect but other species often suffer greatly.

The tortoise beetles are interesting members of the Chrysomelidae because of their resemblance in form to tortoises and in most cases, on account of their golden color, which is lost after death. Some species attack the sweet potato but are not usually serious pests. They are small insects, usually not over a quarter of an inch long, nearly as wide, and often with black markings.