Adults are about 3 mm in length and 2 mm in width. They are flattened and the wing covers and pronotum are dilated laterally forming a broadened lace-like covering of the body. The pronotum is inflated anteriorly into a bulbous “hood” which covers the insect’s head. The outer margin of the pronotum and wing covers bear small pointed spines the nervures of the hood, pronotum and wing covers are also armed with a few spines. The body is black, while the hood, pronotal margins and wing covers are whitish except for an irregular brown spot on each wing cover.
The eggs are barrel-shaped, about 0.17 mm wide and 0.5 mm long and glued to the underside of the leaves. There are 5 nymphal instars. All are armed with spines along the margins of the body and head as well as on the back at different points. These spines are of two main types and quite prominent.
All stages live on the underside of leaves of sycamore where the nymphs and adults pierce leaf cells and extrude the cell contents. The nymphs congregate in groups around the major leaf ribs on the underside of the leaf, toward the leaf petiole. The adults are able to fly but usually only move over short distances. Development from egg to adult takes 35-45 days depending on the temperature.
During winter, adults seek shelter under the bark of plane trees and can withstand temperatures of -10°C. They emerge in spring and breed rapidly when temperatures are increasing and the host trees begin to produce the new season’s leaves.