The mite is found in Asia, Europe and North America, causing abnormal plant growths, known as galls on their primary host, elm trees (Ulmus species).

Partly formed galls are pale yellow patches with irregular lumpy projections on the top surface of the leaf.

The aphids are pink, orange or purple, 2–3 mm long and covered in a thin layer of powdered wax.

[7] In the autumn, winged forms fly to elms and give birth to wingless mites of both sexes.

The leaf reacts by forming a tiny, yellowish pimple on the upper side, which is the early growth of a gall, into which the nymph enters, feeds and produce offspring.