Field and laboratory life cycle studies of Malenka depressa (Banks, 1898) (Plecoptera: Nemouridae)

Abstract

During 1982–1985, laboratory and field studies of 125 eggs, 8055 nymphs and 1426 adults indicated a univoltine slow life cycle for Malenka depressa (Banks, 1898) in a first-order perennial stream in the Mediterranean climate of the San Francisco Bay area. Nymphal growth and adult emergence were continuous throughout the year, further enhanced by a thick, protective tree canopy shading of the canyon that provided an insulated stabilised thermal tube of cool air, ground and stream water temperatures. Leaf senescence of the overhead California bay trees was a perennial source of allochthonous food for the immature stages. Maximum assimilation efficiency for middle to late-nymphal growth stages fed on bay leaves was 42% at 10 °C.