These larvae were found in Mill Creek (tributary to Russian River). They're found in fast, rocky, cooler water. Common March-May. Mature larvae and pupae are about 6 mm long, larval cases and pupal cases 10 mm.
Their case is actually kind of ramshackle for the larvae. Probably because they come out of their case to be swept downstream during their migrations to other areas. Probably in search of more food. They then rebuild the case. On the other hand the pupal cases are relatively strong.