Effect of Photoperiodic Transfer and Brain Surgery on the Photoperiodic Control of Pupal Diapause and Seasonal Morphs in the Swallowtail, Papilio xuthus L.(Lepidoptera : Papilionidae)

Abstract

Larvae of Papilio xuthus were transferred from short-day to long-day conditions at various developmental stages. The critical time, at which the short-day (diapause inducing) effect was cancelled by the following long-day (diapause averting) conditions in 50 per cent of the larvae, was at around the 4th larval ecdysis at 20°C. In the reversed transfer, the critical time was 3 days earlier.In general, there is a close association between the induction of diapause and the spring morph, while the summer morph emerges from non-diapause pupae. This tendency was obscured in the autumnal field population as well as in non-diapause pupae subjected to photoperiodic transfer in the larval stage or to a low temperature during the pupal stage.Association of the seasonal morphs with the developmental pattern was also disturbed by removal of one of the brain lobes, where the mechanisms underlying the photoperiodic control of diapause and seasonal morphs are presumably located.