Latitudinal Variation in Photoperiodic Induction of Pupal Diapause in the Spicebush Swallowtail Butterfly, <i>Papilio troilus</i> (Lepidoptera: Papilionidae).

Abstract

The influence of photoperiod on the induction of facultative diapause was determined for a southern Ohio population of Papilio troilus. We also investigated the extent of population differences in critical photoperiod for induction of diapause for Michigan, Georgia/South Carolina, and Florida P. troilus. Larvae from several families from each population were reared from neonates to pupae under varying photo:scotoperiods on sassafras or red bay foliage with other conditions held constant. The critical photoperiod for diapause was between 14.0 and 14.5h of light in the Ohio population. This compares with 14.5-15.0h for southern Michigan population, 13.5-14.0h for the Georgia/South Carolina population and 12.0-12.5h for the Florida population. Some family-to-family variation in response to photoperiod cues was observed. However, a clear general pattern of higher latitude populations having longer critical photoperiods was evident.