It must be September cuz I'm seeing October caddis

I think I saw my first October caddis of the year the other day. This is good news.
Fishing October caddis dries is kinda like fishing hoppers in that you have big fish eating big flies. More subtlety is required, but it offers similar-sized fish on dries.
Not every river gets a great hatch, but an outstanding emergence isn't required. If you see a couple big orange caddis, tie on an orange Stimulator with stout tippet.
I've mostly fished the hatch on the lower Gallatin, but was told by 20-something fly-shop guy that the Gallatin doesn't actually get October caddis (dicosmoecus). Ok, fella. He said that the Gally (as I'm sure he called it) actually got a bug that looked a lot like an October caddis, but wasn't a real October caddis. It does get that bug (see below), but it also gets the real thing.

And the fact is that for all intents and purposes, they're the same bug. One has lighter wings and is a tad smaller (size 8 to 10), and the real thing has dark wings with a distinct vein pattern (see below), and is size 6 to 8. Note the zig-zag vein going vertically about 2/3 down its side - that's a good way to tell if you've got an actual dicosmoecus.

They hatch in September (I've probably seen more in September than October), just like March browns that hatch in April.

 (cased dicosmoecus larva)

You can fish the pupae as well - just a big orange soft hackle should suffice.
If you see the big orange caddis, tie on a Stimmie and hold on tight.