The A. maculata gall matches an earlier description by Bates (1935). The gall is monothalamous, basically ovoid in shape but usually with an irregular profile due to bracts on the surface (Fig. 3). The entire gall is covered with a thick, white, cottony tomentum. Ten galls ranged from 7.5 to 10.0 mm (Jc = 8.9 mm) at their largest diameter. In cross section there are three distinct tissue layers. The innermost layer is hard surrounded by a thicker, pithy tissue layer which is covered by a thin outer tissue layer. The internal cavity of 10 galls measured 3.0 to 5.0 mm (Jc = 4.35 mm) in length and 1.0 to 3.0 mm (Jc = 1.90 mm) in width. Galls occurring on different subspecies of C. nauseosus are not noticeably different in form. Galls first appear in August as shining green, sticky, globular structures at the axillary buds. At this stage they are not distinguishable from young galls of Aciurina semilucida (Bates) and Aciurina trixa Curran. Within a few weeks they increase in size and a noticeable tomentum forms; although less than half grown, the young galls resemble mature ones. Aciurina maculata gall development is unusual in that growth occurs at a time of year when the plant becomes dormant; most commonly, the growth of galls occurs simultaneously with the growth period of the host (Mani, 1964). In such instances it is not always clear whether the formation of the gall is a mechanical reaction associated with the normal plant growth processes or if the gall-former produces growth stimulation substances. In the case of A. maculata the occurrence of a growth promoting chemical is a distinct possibility. The apparent stimulus for growth is the feeding of an A. maculata larva. Galls grow and develop as long as the gall-former feeds. By fall, when A. maculata has reached the third instar and ceases feeding, the gall is fully formed. Galls with dead A. maculata larvae were found to be consistently smaller than those containing living larvae. A gall may remain attached up to one or two years following emergence. Aciurina maculata galls are found primarily on the lower portions of branches, oftentimes in the adjacent axils of a stem. Also, new galls may form on stems from previous years' growth near the base of the plant. The distribution of galls is often clumped. Galls prevent growth of the affected axillary bud since the tissue of the bud is totally modified in gall formation.

[pg. 714 photo 3 is a monochrome photo of the gall]

- James K. Wangberg: (1981) Gall-Forming Habits of Aciurina Species (Diptera: Tephritidae) on Rabbitbrush (Compositae: Chrysothamnus spp.) in Idaho^©