Noticed a number of these strange creatures in seepage from a spring. The seepage was shallow, mucky, and orange-ish (perhaps from a mix of algae, bacteria, iron and/or...?). The surrounding habitat is mostly open, semi-arid grassland...with a very sparse sprinkling of oaks.

The larva were moving very slowly through the muck. Viewed through close-focus binoculars (or a macro lens) you could see they were energetically waving what appeared to be a short, somewhat circular, "mop" of hairs or cilia attached to the wider end of their bodies.

At first I thought these might be some sort of worm-like organism, but eventually suspected they were fly larvae. Consulting Usinger's "Aquatic Insects of California"(1) reinforced this notion, as did these BugGuide images, the Stratiomyidae pages on the "Tree of Life" web site, and this image from a California Department of Fish and Game website. I'm guessing this may be in the subfamily Stratiomyinae. Then again, maybe it is some sort of worm...or something entirely different?

As always, comments and/or corrections much appreciated.