Morphological comparison of pupal wing cuticle patterns in butterflies.

Butterfly wing color-patterns are determined in the prospective wing tissues during the late larval and early pupal stages. To study the cellular differentiation process of wings, morphological knowledge on pupal wings is prerequisite. Here we systematically examined morphological patterns of the pupal wing cuticular surface in a wide variety of nymphalid butterflies in relation to adult color-patterns. Several kinds of pupal wing patterns corresponding to particular adult color-pattern elements were widely observed in many species. Especially noteworthy were the pupal "focal" spots corresponding to the adult border ocelli system, which were detected in many species of Nymphalinae, Apaturinae, Argynninae, Satyrinae, and Danainae. Striped patterns on the pupal wing cuticle seen in some species of Limenitinae, Ariadnae, and Marpesiinae directly corresponded to those of the adult wings. In Vanessa cardui, eyespot-like pattern elements were tentatively produced during development in the wing tissue underneath the pupal spots and subsequently erased, suggesting a mechanism for producing novel color-patterns in the course of development and evolution. The pupal focal spots reasonably correlated with the adult eyespots in size in Precis orithya and Ypthima argus. We physically damaged the pupal focal spots and their corresponding cells underneath in these species, which abolished or inhibited the formation of the adult eyespots. Taken together, our results clarified that pupal cuticle patterns were often indicative of the adult color-patterns and apparently reflect molecular activity of organizing centers for the adult color-pattern formation at least in nymphalid butterflies.