Oxyna aterrima (Doane) is a univoltine, monophagous, circumnatal tephritid reproducing in galls of terminal and axillary buds on terminal branches of Artemisia tridentata Nuttall. Oviposition occurs in spring (May-June) and the first instars pass the summer (June-September) singly in small, basal, ovoidal cells within the slow-growing, small, clavoidal, uniloculate, bud gall. Second instars occupy their still-small chambers until early winter (December), when they molt to third instars, that then overwinter and grow slowly until the resumption of the spring flush of new plant growth (March). At this time, the third instar enlarges the gall chamber within the still-small gall to accommodate its faster growth and fashions an apical or subapical window for adult egress.

Oxyna aterrima apparently is a true monophage, with Artemisia tridentata as its only known host plant. A composite of the distributions mapped for O. aterrima and O. utahensis in Foote et al. (1993) includes the western states of Arizona, California, Colorado, Idaho, Montana, North Dakota, Oregon, Utah, Washington, and Wyoming as well as the extreme southern parts of the Canadian provinces of Alberta, Saskatchewan, and British Columbia. Allen Norbom (in litt. 2001) also has seen specimens from the Yukon. Thus, the distribution of O. aterrima may coincide wholly with A. tridentata sensu lato, or in part with one or more of its subspecies (Hickman 1993).

...the larval diet consists largely of liquid nutrients translocated to the gall — a foreshortened axillary branch or stem apex (Fig. 8G) — acting as what Harris and Shorthouse (1996) so eloquently have characterized, documented, and explained as a "plant nutrient sink."