The emerging pupa sheds the larval skin, usually intact, and simultaneously attaches itself to the rock by 3-4 pairs of ventrolateral adhesive discs. The entire process usually requires approximately 5-10 minutes. Blepharicerid pupae are well adapted to life in high current velocities, being dorsoventrally compressed and streamlined. Some rocks may harbor hundreds of pupae, most oriented in the same direction. The pattern of suctorial-disc attachment and general movement of larvae are complex, behavior dependent, and predictable.
Diatoms appear to be the major component of their diet.
The duration of the pupal stage varies with species and stream temperature, but usually lasts between 2-3 weeks. Emergence of the adult requires that the pupa is attached firmly to the substrate. Thoracic sutures are ruptured by downward pressure from legs and wings, and the emerging adult usually reaches the stream surface in an air bubble. Emergence can be quite brief, requiring from 3-5 minutes. Some species emerge at night or during dawn or dusk, but many species emerge primarily during the day.