The larvae are typical, white or cream-colored, legless grubs, about the same size as adults. Beetle feeding at twig crotch. Identifying the Injury. Larval mines are roughly perpendicular to the egg gallery. The result is a design resembling a long-legged centipede on the inner bark and wood surface.
Adults feed at twig crotches of healthy elms, infecting the tree with Dutch elm disease.
Then they fly on to other elms for breeding. These attacked trees have usually been weakened by drought, disease, or other stress factors. After boring through the bark, the beetles excavate their egg galleries, grooving the inner bark and wood surface in the process. When larvae are full-grown, they construct pupal cells at the end of their larval mines. There are two generations annually.