Lasioptera impatientifolia
(Cecidomyia impatientis)

On petiole or midrib, on both sides. 1 cm. long, 4 mm. wide. Green, smooth, monothalamous, containing several larvae. On Impatiens biflora.

Common.

Gagné (2004) synonymized Neolasioptera fulva with Neolasioptera impatientifolia, however these two species are clearly morphologically different as larvae. Two main differences occur. ... Gall formation in Neolasioptera impatientifolia occurs on leaf veins, while galls of Neolasioptera fulva* are found on the main stem and branchlets.

[Gallformers.org follows the Gagné & Jaschhof (2021) checklist, which again synonymizes Neolasioptera fulva under N. impatientifolia.]

Swollen midrib or petiole...Neolasioptera impatientifolia (Felt)

Swellings are usually more visible from beneath the leaves, are succulent, partly translucent, light green, and contain one to several larvae and an associated fungus...Hosts: I. capensis, I. pallida