The life cycle of Stenocolus scutellaris includes oviposition in summer, larval growth and overwintering for at least two years, pupation in late spring and adult emergence in summer. the larval food mainly includes FPOM, shredded wood, algal filaments and associated debris; adults do not feed. The geographic distribution is in California's Central Valley counties, in the Sacramento/San Joaquin River systems. Various parts of the morphology of the egg, larva, pupa and adult are described and illustrated. The larval “gills” are shown to be osmoregulatory structures, not respiratory structures.