[Felt is describing the leaf gall; use arrows at right for flower gall description]

A somewhat flask-shaped or subconical, solitary or confluent white pubescent leaf gall, diameter at base 2 mm., height 3 mm. ... [T]he basal portion of the gall [is] thick-walled, with an oval cell having a length of about 1.5 mm. and a distal tubular, thin-walled portion separated from the larval cell only by a thin, matted layer of filaments, the top being light filled with a curled, woolly mass.

This species has two generations per year. The summer generation develops in galls principally on ephemeral leaves while the overwintering generation develops in galls on flower buds.

The flower bud gall of the overwintering generation is not readily visible. The affected buds remain closed during bloom and the gall can be found only be forcing open the involucral bracts. An elongate sclerenchymatous larval capsule with a dense covering of long white trichomes replaces the flower. During the period of full bloom the capsule is green but after bloom the gall becomes translucent and colored much like that of the dry involucral bracts. By the summer following adult emergence, all galls have dropped from the plant. The few mature galls measured were approximately 2 mm in length and 1 mm in width. [Description about biology and seasonal occurrence of the summer generation gall is given but no description of the gall itself is provided. It is shown in Figure 16 later in the paper however.]

Rhopalomyia ampullaria
Urn Gall Midge

These tubular galls may occur singly or in coalesced clusters of two or three, usually protruding at right angles from the host leaf.

Gall on leaves...
Gall sessile...
Gall convex at apex...
Gall 2–7 mm long
Gall conical, on Artemisia tridentata...Rhopalomyia ampullaria Felt

These galls occur mainly on ephemeral leaves, occasionally on stems and flower bracts. This gall midge has two generations per year, the overwintering one developing in galled flowers, the summer generation in the conical galls on stems and ephemeral leaves.