The Effect of Constant and Varying Temperatures on the Development of Acanthocyclops viridis (Jurine)

1. Experiments were carried out on Acanthocyclops viridis (Jurine) to determine the duration of the egg stage and the length of the various larval stages at constant temperatures varying from 10°C to 30°C. It was found that while the duration of the various stages was shorter at higher temperatures each stage was not affected to the same extent. For instance the duration of the egg stage was shortest at 30° whereas the duration of the third nauplius stage was shortest at 21·8°. 2. A number of experiments were carried out in which the temperature was continually changing during development. Calculations based on the constant temperature experiments showed that the duration of the development from the time the egg was laid until the end of the 5th nauplius stage was shortened due to the alterations of temperature. The acceleration was small and amounted to 12·2%. 3. Similar experiments with the copepodid stages showed that alterations of temperature had no effect on the developmental rate.