Sex-limited variability mimicry in the swallowtail butterfly Papilio polyxenes Fabr.

Abstract

Variation in wing pattern was measured in the swallowtail butterfly Papilio polyxenes, a Batesian mimic of the butterfly Battus philenor. Males and females differed in the number of yellow spots comprising the proximal spot band on the dorsal surfaces of the wings, with females having fewer spots than do males. This difference results in females being more similar to B. philenor than are males. However, females were also more variable in spot number than were males. Full sib analysis of variance of females and regression of daughters on mothers indicates that variation in spot number is heritable. The ventral surfaces of the wings of males and females showed little variability and were similar to those of B. philenor, suggesting that the adaptive significance of the dorsal surface wing pattern differs in males and females. Possible reasons for such a difference are discussed and a model based on the genetics of mimicry in P. polyxenes and developmental studies of wing pattern formation in butterflies is proposed to account for the suppression of variability in male wing pattern.