I live in Eastern WA & was at a creek the other day. The person w/me said the things i was finding were "pennywinkles." The stick to rocks lightly, cover themselves in sand & it looks like they hide in their "home" like a snail. When they come out of the "shell" (about 1/2"-1" long), they are black, eith little feet & don't bite. When they die, the shells are left, so I collected some- very neat. But I'm not finding anything on "pennywinkles". Also, they don't come fully out of their shells & they stay in the water, on rocks and at the bottom- they don't swim. What are these called?
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They are caddishfly larvae (Trichoptera).