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.

Larve form 5 mm blisters on the upper sides of boxwood leaves. The species, an immigrant from Europe, was introduced into North America during colonial times with potted boxwood.