Pupal exuvia were found on a gall on May 27, 1969 at Site 3. Adults were reared April 21-26, 1972 from galls collected April 18 at Site 15.

This monothalamous gall appears to be associated with one of the first ephemeral leaves that develop in the bud. The mature gall consists of a long, thin erect stalk with an enlarged apex made up of the fused lobes of the leaf tip (Fig. 18) surrounding a sclerenchymatous larval capsule. Some galls have a whorl of spatulate leaves at the base of the stalk. Two galls that were measured had stalks 10 mm long and the enlarged apical portions 5 mm long by 2 mm wide.

Gall a flowerlike swelling at end of long, narrow, deformed ephemeral leaf...Rhopalomyia culmata Gagné

The gall, about 5 mm long at the apex of a 10 mm long stalk, occurs only on ephemeral leaves that develop in spring...Host: A. tridentata