Über die Wirkung der Photoperiode auf den Schlüpfrhythmus der Falter vonSpodoptera littoralis Boisd. (Lep., Noctuidae)

Abstract

Effect of photoperiod on emergence rhythm of adult Spodoptera littoralis Bolsd. (Lep., Noctuidae) Adult emergence ofSpodoptera littoralis Boisd. from pupae, reared since the egg stage at different photoperiodic conditions was studied. The photoperiods tested were: 8 hours light and 16 hours darkness (8L:16D), 10L:14D, 12L:12D, 16L:8D together with continuous light (24L:0D) and complete darkness (0L:24D), In the shortest day-length (8L:16D) all adults emerged at night, while in the longest one (16L:8D) 40%) only emerged during the dark period of the day. In the intermediate photoperiods, the percentage of the light-emerging moths increased with the prolongation of the photophase, thus at the photoperiods of 10L:14D, 12L:12D and 14L:10D such percentages were 9, 13 and 28 respectively. In cases where insects were reared in continuous light (24L:0D) or complete darkness (0L:24D), emergence took place at random and the rhythmicity disappeared. By transferring newly formed pupae, reared in complete darkness, to photoperiod of 12L:12D, adults emerged mainly during the dark phase (90%). On the other hand, when pupae reared in 12L:12D were transferred to complete darkness emergence took place at random (arrhythmic emergence). This indicates that the pupal stage is the sensitive one to phase regulation and not the larval stage.