I'm guessing this is a male (because of the wing tooth) Pterodontia misella. I do not know the exact date, since I collected 4 specimens (and found another dead on the ground) between April 26th and May 19th 2011, and failed to keep the data separated. The dates for the individual specimens are:
April 26th, 2011 (on a poplar, I believe),
May 2nd 2011 (found dead on the ground),
May 11th on a rose bush,
May 12th on an aphid-infested apple tree, and
May 19th on a rose bush.
I saved all the specimens I found, as they seemed very strange to me at the time. I couldn't seem to find the family with Borror and White's Field Guide to the Insects (1970). I believe because Borror's representative veination illustrations were quite differant from my specimens (that is what I remember, I don't have the book to check though). After a while I started wondering if it was a small-headed fly because of the (obviously!) strangely small head. More recently (probably last year), I was able to identify them (at least tentatively) to Pterodontia using the photos in the guide. Just this week, I noticed Arthur Macmillan's recent sighting from SLO County, and it struck me as rather similar to my specimens, and inspired me to get this photographed and posted.
The immediate "habitat" might be characterized as rural residential, with lots at least 1 acre or larger. The lots are usually mown, landscaped, grazed, or native; but there are islands of blue oak grassland and sparse blue-oak woodland, including about 25 acres of undeveloped land literally a few hundred feet away from the location of this sighting. Areas surrounding the residential area are either vineyards or native grassland/coyote brush.
Very coincidently, I discovered a female specimen (it laid a large number of tiny eggs), just yesterday, a few hours after some of my commenting on Arthur Macmillan's recent Pterodontia misella post! I have photographed it, and the photographs are posted here:
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The photos in this series were brightened for me by Aaron Schusteff.