The influence of photoperiod on the life-cycle of Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae)

Abstract

Diapause in fully grown larvae of Ectomyelois ceratoniae was induced by low temperature and short photoperiods. When larvae were reared at 30°C, 70% r.h. there was no diapause in a light regime of 12 hr light followed by 12 hr darkness ( 12 L 12 D ), and only 20% entered a weak diapause in continuous darkness. However, at 20°C, 70% r.h. there was no diapause in 16 L 8 D but almost all larvae entered diapause in 12 L 12 D . At 20°C diapause delayed adult emergence by an average of 111 days, compared with about 50 days at 30°C. Survival to adult at 30°C was 75% or more at most photoperiods, but at 12 L 12 D and 13 L 11 D it was less than 50%. At 20°C survival was about 70% at the two photoperiods tested. A slight effect of photoperiod on non-diapause growth rates was observed. Above 16 hr light longer photoperiods reduced the mean developmental period from egg hatch to adult emergence, by 4 days at 20 L 4 D and 6 days at 24 L 0 D . The significance of diapause in this species in relation to its potential as a pest is discussed.