A small, delicate fly. Damage is caused by larvae which feed between the upper and lower layers of leaves. Two to six larvae typically occur in a single leaf. With a little practice, they are easily found by breaking open a blistered leaf with your thumbnail. Adults are rarely seen.
Nymphs cover themselves with white, cotton-like secretions.
Mites overwinter as eggs on the undersides of leaves. Larvae overwinter within their mines. Nymphs soon cover themselves with white, cotton-like secretions.