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Abstract
The photoperiodic and thermoperiodic response of larval growth in Planotortrix octo Dugdale was tested by rearing larvae under constant and fluctuating temperatures. The relative contribution of long and short days in influencing larval development was also tested by transferring larvae from long to short days and vice versa.
Compared with development under a constant temperature and 12 h photoperiod, development was faster when the cryophase of a thermoperiod coincided with the light phase, and slower when the cryophase and scotophase coincided. This provides further support for a photoperiodic mechanism controlling larval development in this species.
Under long-and short-day thermoperiods in total darkness, development was slower when the cryophase was colder, even though the average temperatures were the same. There was no suggestion of a thermoperiodic effect.
When larvae were transferred from long to short days or vice versa, larvae that had experienced long-day conditions during part of their larval life developed faster. This suggests that long days have a stronger influence on larval development.