Laboratory studies on the larval biology of Simulium venustum Say (Diptera: Simuliidae)

Larvae reared from field-collected eggs of Simulium venustum were found to pass through six larval instars. Temperature strongly affected both the growth rate of larvae and their survival. At 5, 10, and 12 °C all S. venustum larvae died before reaching the sixth instar. At 15 °C, larvae were found to be able to complete development to the sixth instar, although only 10.5% survived to this stage. Increases in temperature led to increases in survival and rate of growth, with the best survival (20.4%) at 22 °C; most larvae required 22 days to reach this stage. Above 22 °C, survival decreased (5.7%), although the growth rate continued to increase. A growth model for blackfly larvae simulating natural conditions was constructed using temperature–growth curves obtained in laboratory trials and comparing these data with stream temperature profiles.