I've been looking for the gall of the coyote brush stem gall midge (Rhopalomyia baccharis
) that Russo talks about on pp. 240-242 of Field Guide to Plant Galls of California and Other Western States
, and I think I might have found one today. It was a visible thickening toward the end of a dead stem on a coyote brush (Baccharis pilularis
). It appeared to be old and dried out; I removed it and brought it home for closer inspection.
This image shows the general dimensions of the gall, which appears to match pretty closely Russo's description of "50 to 90 mm long by 5 to 8 mm in diameter". I think I might also be seeing the unusually shaped elliptical openings at the outer, distal ends of the larval chambers that Russo describes.
The section of stem shown here grew from left to right (that is, the outer end of the stem is the end toward the right). The other R. baccharis
photos currently on Bugguide show the gall on a living stem, but besides the desiccation of this gall, it looks like a pretty close match. See:
I was thinking about cutting it open to see if I could expose the larval chambers depicted by Russo's cutaway illustration, but I haven't tried that yet. In the meantime, I'd appreciate comments from anyone familiar with the appearance of these galls. Thanks.