Found at a muddy-edged desert pond...what appeared to be an old, abandoned cattle-watering reservoir, artificially constructed by man (or at least enhanced), but "well-naturalized" with surrounding vegetation. This syrphid was visiting dilapidated flowers in the leaf axils of a tumbleweed (Salsola tragus), where it appeared to be feeding on nectar.

I immediately recognized this in the field as a syrphid in Cerioidini...rather than a conopid!...having been fooled before (and learned) while previously working on Mark's post below:

   

In fact, I initially thought (it turned out correctly) that this might be Polybiomyia townsendi...but, in keying it later from my photos using the MND(1) and CJAI(2), it seemed to me that I could make out a non-chitinous membranous patch between the hind coxae in the 2nd image of this series, and that's the technical character that distinguishes Sphiximorpha from Polybiomyia. (Turns out I was mistaken in thinking that might be the post-metacoxal bridge, which is not visible in any of my photos here.)

I continued to search out literature on Cerioidini, and found that in a number of author's keys and treatments, the only good Sphiximorpha candidates (i.e. Ceriodes (=Sphiximorpha) durani and Ceria (=Sphiximorpha) cylindrica, both recorded only from CA) had numerous inconsistencies with my photos in going through the available keys and descriptions.

Finally, I used the 1924 key of Curran for Cerioides (a group which at that time contained both the currently named S. cylindrica and P. townsendi), and saw that my individual here clearly went to Cerioides (=Polybiomyia) townsendi. What clinched the ID was the excellent agreement between not only Snow's original 1887 description of Ceria (=Polybiomyia) townsendi, but the even more detailed 1924 redescription of C. townsendi by Curran. In particular, Curran pointed out that the base color of the abdomen can be variable...from mostly black to mostly dark reddish. Previous to reading that I was somewhat doubtful of the ID, due to that fact that the base color of the abdomen in the individual in my photos was black...in contrast to Snow's description of townsendi as a "red species", which is in accord with Mark's thumbnailed image above...and also with Gerald Donahew's post from Texas below:

   

Further reinforcement for the ID of P. townsendi here comes from the citation in Cole(3) of a record (with "general color black") from "Ivanpah, San Bernardino Co., Calif."...that being the only specific CA record I could find anywhere. Ivanpah is only a few miles away from the locale here.

Note that a number of references I browsed stated that males in Cerioidini have holoptic eyes (unlike their somewhat similar looking conopid cousins) and females have dichoptic eyes. So this is a female. At the time of this post, few if any previous posts in this group have gender indicated. That can now easily be done for many posts, knowing the above.