¹Department of Zoology, University of Stockholm, 106 91 Stockholm, Sweden and Department of Biology, University of Antwerp (UIA), Universiteitsplein 1, 2610 Antwerpen, Belgium

Correspondence: Jack J Windig, Department of Zoology, University of Stockholm, 106 91 Stockholm, Sweden. E-mail: jack.windig@zoologi.su.se

Received 16 March 1998; Accepted 14 July 1998.

Abstract

Effects of melanization in the juvenile stages of the European map butterfly (Araschnia levana) and the peacock butterfly (Inachis io) on the life history traits, larval and pupal development time and size at maturity, and on adult melanization were investigated. Pupae and 5th instar larvae of A. levana vary in degree of melanization, the latter possibly determined by a single major gene. Variation in melanization in I. io occurs only in the pupal stage and is under low genetic control. In both species life history traits and adult melanization are influenced by juvenile melanization, both at phenotypic and genetic levels. Many of the relationships are consistent with trade-offs, e.g. melanized 5th instars of A. levana grow more slowly in early instars and I. io adults from melanized pupae are smaller and less black. However, some results are inconsistent with a trade-off hypothesis. Possible adaptive and physiological explanations are discussed. Araschnia levana shows seasonal polyphenism in wing pattern; pale larvae produced more spring forms, probably resulting from slower growth in the 5th instar. Genetic correlations across environments for larval development time and adult size are to a large extent influenced by larval melanization.