And now a word (or two) from Fred

Photo by Ned Harris 10/18/11

Ned, Carol T and I were out and about on patrol in the canyon on Tuesday; met a lot of inquisitive out-of-towners - and may have helped sell a few hats from the bookstore. Another day in paradise.
(You'll want to click on the photo for a bigger view.) Ned asked Fred Heath for an i.d. on this butterfly, and Fred was happy to oblige. Some excerpts:

Very interesting photo!! The butterfly is a Ceraunus Blue (Hemiargus ceraunus) which somewhat resembles a Marine Blue with [fewer] and less obvious markings. It is nectaring on Dalea Dalea pringlei. This species is known to use various legumes as food plants (what the caterpillar eats), although I don’t know that a Dalea has been recorded as a food plant.
What is interesting is the fact that there is well camouflaged caterpillar in your photo which could well be a Ceraunus Blue. If you look just above and slightly to the right of the base of the flower you will see a slug-like creature which is off-white with brownish markings. I will send a copy of this photo to our local expert Jim Brock to ID if possible (it could be Marine or Reakirt’s Blue as well since they all look similar and usually are colored and patterned to match the host plant somewhat). I will let you what he thinks.  [time passes...]  After checking with Jim Brock, it looks like the caterpillar will have to remain a mystery blue. Since the caterpillars of these small blues look so similar, he says the only way to tell for sure is to raise the caterpillar to adulthood. 

Thanks, Fred