This one was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.
This tiny little caddis larva was pumped from a small canyon stream brown trout stomach:
From the curled abdomen I was guessing it's Helicopsyche. Why is it out of its case? It looks too intact to have already had the case digested, although maybe the silk bound sand grains dissolve quickly. They shouldn't drift case-less as I believe they continue adding on the the same case. Anyway, thought I'd share it.
After looking at images of Helico, it doesn't look like it is. Too young to tell? It's tiny, like #28. Heck of a set of grippers eh? How about a very young Rhyacophilia -colors are right for it?
I have never seen a green bodied Helicopsyche larva and legs don't look right. Do you think those black areas at apex of abdomen are large and sclerotized? If so, that is too many for Rhyacophila. Was it Bear Creek? lateinstar Leucotrichia?
This is the only image I have. The end of the abdomen looks sclerotized to me. It was from Middle St Vrain canyon at about 6500ft -the trout from a seething pocket water pool. Late instar would seem timely wouldn't it? Leucotrichia? But the abdomen is not very wide.
Sorry, by late instar I did not mean last instar. Should have said penultimate. And as Kurt implied - size already helps. Early instar caddis in general look quite different than the final instar. Early instar hydroptilids are no exception and have the typical, slightly tapered caddis abdomens rather than the enlarged abdomen. Very few figures/pictures are available in the NA literature. Do you have access to Hicken 1968? Wiggins 1996 has Leucotrichia.
In your specimen there looks like more than the single sclerotized apical plate typical of Rhyacophila. That led me to Leucotrichia, or a terrestrial larva like a beetle. If you don't have the specimen we will never know.
I don't have the specimen. Nor Hicken. It does look like there are more than a single apical plate. The size is what surprised me. Leuctrichia is probably best bet, but we'll never know I guess. Thanks for the responses guys.
The earlier instar would also explain the lack of case as well, Paul. As to what it is, I'm no closer than I was before and I wouldn't hazard a guess as to genus, but I do agree with Dave that it's probably a hydroptilid (Microcaddis) of some kind.
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman