Cecidomyiidae

Rhopalomyia

Artemisia tridentata

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Rhopalomyia anthoides

The bud galls of R. anthoides superficially resemble those of R. florella. 

Immature larvae were found June 10, 1968 at Site 15 coinciding with the first sign of gall development. The larvae appeared to have reached maturity by late November or early December and completely filled their individual sclerenchymatous capsules. 

This bud gall has a seasonal occurrence similar to that of R. cramboides. In appearance it differs by being longer and less rounded and in structure by having the leaves composing the rosette more linear. In addition, the long outer leaves surround the shorter leaves of the gall base. All leaves of this gall on A. t. wyomingensis have a proliferation of long trichomes especially at their base (Fig. 27) while the leaves on A. t. vaseyana gall have trichome proliferation only on the inner leaves. 

Eighty-four mature galls from A. t. wyomingensis at Sites 15 and 16 had a basal diameter ranging from 4-15 mm (avg. 8) and a height (length of outer leaves) ranging from 5-17 mm (avg. 11). Fifty-nine of these galls had 1-49 sclerenchymatous larval capsules (avg. 4). 

Developing galls differ from mature galls mainly in size. Maximum size of the gall appears to be attained by winter. Following adult emergence in spring the galls dry out and darken in color but persist on the plant a year or longer. 

Biology and taxonomy of the Rhopalomyia Gall Midges (Diptera: Cecidomyiidae) of Artemisia tridentata Nuttall (Compositae) in Idaho

Rhopalomyia anthoides 
Leaf-bud Gall Midge

This midge induces monothalamous bud galls on Great Basin sagebrush that are composed of numerous compact, narrow bracts. 

Plant Galls of the Western United States