Greenish, wax-covered poplar stemgall aphids, Pemphigus populicaulis, exposed inside the globular, yellowish green to cream-colored gall formed by their feeding at the base of the leaf blade.
Greenish, wax-covered poplar stemgall aphids, Pemphigus populicaulis, exposed inside the globular, yellowish green to cream-colored gall formed by their feeding at the base of the leaf blade. Credit: Jack Kelly Clark