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Coyote Brush Bud Gall Midge - Rhopalomyia californica

Coyote Brush Bud Gall Midge - Rhopalomyia californica
Boulder Creek, Santa Cruz County, California, USA
March 28, 2010

Images of this individual: tag all
Coyote Brush Bud Gall Midge - Rhopalomyia californica Coyote Brush Bud Gall Midge - Rhopalomyia californica Coyote Brush Bud Gall Midge - Rhopalomyia californica Coyote Brush Bud Gall Midge - Rhopalomyia californica

Oh, wow
I've been interested in seeing this happen for years. I always try to check the galls on our local coyote brush, but have never (until now) known what it looks like when the adults emerge (or even what the adults look like).

According to the abstract for Portrait of an Ephemeral Adult Stage: Egg Maturation, Oviposition, and Longevity of the Gall Midge Rhopalomyia californica (Diptera: Cecidomyiidae), the adults emerge, mate, lay their eggs, and die, all within a 24-hour period (on warm days, as little as a 5- to 6-hour period). I assume that means that they must all try to emerge at approximately the same time.

I just realized that this image I took on March 29 (the day after the emergence you photographed here) could well have been a R. californica: Unidentified dipterid on my desk. I had been out hiking at the Carpinteria bluffs, around a lot of coyote brush with R. californica galls on it. If we can assume that midges in Santa Cruz County and Santa Barbara County might have been emerging at approximately the same time, it would make sense that one hitchhiked back from the bluffs to my office on my clothing. I wish I'd paid more attention to the galls during my hike!

Thank you so much for posting these amazing images.

Bad break for midges?
Thank you for the nice comments. Sorry it has taken me so long to respond.

I didn't realize it at the time I took the photos, but later it became apparent that those midges were dead. My guess is that the weather here in March when they emerged was too cold and they didn't make it. Thus they were "frozen in time" enabling me to get emergence photos. (No wonder they were so cooperative about holding still for the multiple images needed to make extended depth of focus stacks!)

A few days later I was on a hike in Big Basin State Park and checked the Coyote Brush for galls. I found some near the coast in the same state even though the climate there was more moderate than at my house (at 1000 feet) where the posted photos were taken. But I am still sticking to my theory that we had a cold snap and figure it included both sites.

Hm. Dead? Or Exuviae?
I'm not sure these are dead midges. I think they might be the spent exuviae left behind after the adult midge emerges from the pupal case. I photographed some mayfly exuviae a while back, and they looked somewhat like this. See:

In Russo's Field Guide to Plant Galls of California and Other Western States, he writes: "When fully grown, larvae burrow to the surface of the galls, where they develop their partially protruding white cocoons and pupate" (pp. 238-9). In the discussion of a related species (R. baccharis), which forms stem galls on the same plant, Russo writes of "its relatives [presumably including R. californica] in which the pupae partially push their way out of the gall before the adult emerges" (p. 242).

Tilden's 1951 paper, "Observations on Rhopalomyia californica Felt (Diptera, Itonididae)", from Pan-Pacific Entomologist XXVII(1):20-22, sounds like it would be a worthwhile place to get more detail. Now, if only all the entomology journal articles from the last 60 years had managed to make their way onto the Web, I'd be all set. :-)

And thank you
for the link. I added it to the info page.

Nice shot!
Welcome to Bugguide. You could link all these images by tagging them, they will show up at the left, and then clicking on "link".
Do you have other close-ups of this emerging midge?

More photos
I have created a small album (nine photos) at . The images there are 1200 x 900 pixels in extent.

If anyone is interested in the imaging stacking process used to create most of those images there is an album at that describes the procedure.

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