Polymorphism is common in nature, but few Heliconius species are polymorphic for wing colour patterns. Eastern Brazil H. erato phyllis populations are polymorphic for hindwing elements (red raylets) and studies suggest that trait distribution varies seasonally. We carried a 3-y sampling to evaluate the hypothesis that season, wing length and pollen foraging were associated with morph diversity. Individual phenotypes were scored with regards to number of red elements in the dry and in the wet seasons. Co-mimic H. melpomene nanna was also analysed. We scored 432 H. erato and 513 H. melpomene. Our results confirm polymorphism in H. erato, with individuals showing from one to eight elements, with a mode between five and six. We found that H. melpomene is polymorphic for red dots, varying from two to five (mode = 2). Red basal dots were mostly invariant in H. erato. Even though we found a seasonal change in pollen loads, we found no association between individual phenotypes and season, pollen load scores, or wing length. We reject the hypothesis of ecological correlates of morph frequency, and suggest that trait colour variation in the two species is linked to and constrained by effects on mate recognition.

We studied the effect of morphological variation and basking posture on thermal characteristics in the speckled wood butterfly Pararge aegeria (L.). The process of heating and cooling in relation to wing type (descaled, darkened and original wing colour) and size was examined using dummies (i.e. dried butterflies). Size (measured as wing length) and ambient temperature have a joint influence on body temperature: large butterflies heat up more slowly than small ones, but with increasing ambient temperature the difference with size became smaller and even changed since large individuals heated up faster under warm ambient conditions. Surprisingly, darkening wings had no overall effect on thermal characteristics, but this may be an artefact of the manipulation as supported by the results of the absorption measurements. Normal butterflies reached a higher equilibrium thoracic temperature than descaled butterflies probably because wings without scales absorb less radiation. Finally, butterflies with fully spread wings reached higher thoracic temperature and had faster cooling rates compared to butterflies with half-opened wings. Implications of the results for the relation between morphology and behaviour of speckled wood butterflies in their natural habitat are discussed.