Please click to the last picture, #293513, for comments on the CU Museum and Library visit.

We blew up those three cells in photoshop and finally decided that it was the underwing the was causing the curve that looked like the 3rd cell. It was a tough call, though. The second photo, which as I said, may not be of the same bee, shows only two. However, the legs seem similar. All black insects just don't show detail.

"The second photo, which as I said, may not be of the same bee, shows only two"

No, both images clearly shows three submarginal cells in the left wing and two in the right wing, so it must be the same individual.

"it was the underwing the was causing the curve that looked like the 3rd cell"

No, in both images the underwing is faintly visible in a different position. Also, the underwing would not show the same illusion in two photos.

This must be a rophitine of one of the three-celled genera with loss of a crossvein in the right wing.

The large reported size is consistent with Xeralictus timberlakei.

An interesting webpage on Xeralictus:
http://entmuseum.ucr.edu/bug_spotlight/posted%20Images-pages/33.htm

Thanks so much for all the information. I checked Krombein et al and see that X. timberlaki is an oligolege of Mentzelia involucrata. I checked out the website you gave me with M. involucrata and its mimic Mohavea confertiflora. I know both these flowers! Both occur in Anza-Borrego, where rocky slope meets desert floor. We have seen these flowers in Borrego Valley--but never in the Scissors Crossing area where we saw these bees. The terrain was very similar, though. I checked the San Diego flora and both flowers could occur where we saw these bees.

I checked the CU Museum entomology collection, which is on line, and it has a specimen of each of the two species of Xeralictus, though I don't know if male or female. On our next visit there in about a month or so we will bring our photos and try to check them out feature for feature.

It's very exciting to think we may have this bee. Thanks so much for all your help. We appreciate it so very much.

thanks for posting these photos

Note spelling: Xeralictus = xeric Halictus

I don't think this is a Xeralictus so am not sure what it is

I just posted what I think is the best image of this bee, #293513. It shows a lot more than the other photos. On Friday we plan to visit the CU Museum Entomology Collection, where I will try to check out this bee trait by trait with their Xeralictus.

I posted the last image we have of this bee, though I don't think it shows anything new. We'll be on the lookout for this bee again, and maybe will be able to get more diagnostic pictures.