**Description:** An aquatic larva that builds a specialized home out of sand grains shaped exactly like a spiral snail shell.
**Size:** The spiral case is roughly 0.1 to 0.2 inches wide.
**Behavior:** The heavy sand-case acts as ballast, allowing the larva to graze on algae in torrential currents without being swept away.
**Identification:** Their presence is a sign of high water quality and an undisturbed, oxygen-rich stream bed.
**Habitat:** Fastest-moving riffles of clear mountain brooks.