Photoperiodic control of larval development rate in Planotortrix excessana (Lepidoptera: Tortricidae): Evidence for larval diapause

Abstract

The larval development rate and pupal weights of Planotortrix excessana Walker were monitored under seven different 24 h photoperiods. Larvae developed through 5–7 instars with the extra instars being most common in females. Photoperiod had a significant effect on the duration of all instars, total larval period, and number of instars.

The response for both larval duration and instar number was typical of insects in which diapause occurs during long days. Evidence for the presence of a photoperiodically induced diapause is discussed. Disturbance of larvae during head-capsule measurement significantly reduced pupal weight in both sexes but had no effect on larval duration.

Keywords:

• Diapause
• development
• photoperiod
• Lepidoptera
• Tortricidae
• Planotortrix excessana