Thanks a bunch for the ID! I gather from the number of recent moves of Toxophora to species that the taxonomy of this genus has been revised. I'll update the taxon on our field station invert list.

No real revision although Cunha et al. published a key last year in Zootaxa. The key isn't very useful for separating a few species from photos, but I went through the Toxophora at the CNC yesterday and that clarified things.

I searched online for information about local Toxophora species and found that the Sixth Report of the Laguna Marine Laboratory and Contributions from the Zoological Laboratory of Pomona College (1918) lists the Diptera of the Pomona Zoology Department Insect Collection and includes Toxophora pellucida (collected from "mountains near Claremont") and no other Toxophora. Unfortunately the insect collection was lost somewhere along the way, so we cannot compare specimens, but it shows that the species was in this area.

(As a point of information, the Zoology Department no longer exists, having been merged with Botany to form the Biology Department.)

last night (1:22AM PDT)? I landed on T. pellucida by using Coquillett's key (West American Scientist 7(61):199-200,1891).
There could well be other spp. in the area, but pellucida best fits the descriptions.
By the way, I looked at lots of other leads, rather frustrating, also finally noticed that most references give the wrong issue (62) of West American Scientist. There are a number of issues with this genus and, as Joel has already remarked, it is in need of revision.
I'm also checking with Doug Yanega regarding specimens at UCI.

I don't think this is T. pellucida. That species should have the dm-cu crossvein angular with a stump of vein M2 (see here for a similar species); I think it also has more white than this fly. The closest I can get for this one is T. maxima, but it seems to have complete black bands on the abdomen unlike the description of that species. That may be variation, or this could be an undescribed species; with the last review 120 years ago I wouldn't be surprised if there are new species in this genus.

He also felt that it could well be T. maxima, based on specimens of both spp. identified by Jack Hall, i.e. "the strong yellow coloration of the tail, and the unbroken bands on the anterior abdominal segments, are more typical of T. maxima."

Thanks for the information! I see what you mean about the vein. I'll put this on our list as Toxophora sp. We'll see if we can collect a specimen, but this individual is the only one I've seen so far. It would be cool if we had a new species! Is anyone working on revision of this genus?

I'm not aware of anyone working on the Nearctic Toxophora.

Thanks! Most of the credit goes to the very cooperative fly, which sat still for so long. I wish all insects would be so accommodating!

I had a bot fly land on my beat sheet yesterday just after I had beaten some branches and was looking for beetles. As I attempted to very gently place the beat sheet down, it took off like a shot. :-(