My pleasure, Paul. I really enjoy this stuff. Just to clarify from Dave's helpful comments, I hope I didn't lead you to believe I think your photos are of either another family or paradoxically the species I referred to. I should have been more clear that I agreed with your assessment they probably represent the genus Lepidostoma
. I mentioned the species only because you asked about experiences with the genus, so I thought I'd share one of mine. As for the cases, I have seen photos in the record that blur the lines enough for my limited abilities (specifically Merritt IV among others) that without a look at the larvae, I felt the need to qualify my opinion. If an expert like Dave is confident that they aren't the optional possibility I gave, that's certainly good enough for me.
I should have also added that as a genus they are widely distributed and are in my opinion probably the best "dry fly" caddis I've fished over. They are certainly the most "mayfly like" in my experience, spending a fair amount of time on the surface both emerging and egg-laying, and they do so fairly sedately (for a caddis:)). However, I don't recall seeing them in the numbers on freestone streams that rival what I've seen on Spring Creeks, particularly the example I gave.
I have Ward and Kondratieff (1992) Mountain Stream Insects of Colorado and they state that then-available larval keys are not sufficient to the species level.
Hopefully Dave has more to share on this, but that's largely my understanding as well. Though there are a few species that can be identified by unique larval characters, most are placed in groups based on case design as follows:
1. Panel case (often four sided like Brachycentrus
but with panels looking a little like small Phryganea
2. Turret case ( stuff sticking out all over. ex. podagrum
, see photos)
3. Sand case (your specimens probably belong to this group)
4. Pluviale (similar to the sand case, but more tapered and more curved)
5. Tube (similar to the sand case, but without curve)
For case examples that blur the lines in the last three groups, head capsule characters and presence or lack of gills are further aids in differentiating them.