Globular leaf swelling...Schizomyia sp.
Swellings are thin-walled and monothalamous, slightly discolored, about 5 mm in diameter. When full-grown, the active, orange larvae break out of the gall and drop to the soil to pupate...Host: A. artemisiifolia
”- Raymond J. Gagne: (1989) The plant-feeding gall midges of North America©