Checking billy barr’s snow log…
1. Alba, a white wing colour morph of butterflies of the genus Colias, makes fitness‐related changes at several levels of phenotypic organization: physiology, development and behaviour. Two sympatric species of Colias are studied, which differ greatly in their frequency of alba vs its sister yellow/orange morph. How resource and time constraints on Colias interact with the morphs’ different patterns of pupal resource allocation to alter the balance of the morphs’ fitness components in the two species is discussed. 2. These species, C. alexandra and C. scudderi, differ in melanin‐based solar energy absorption, in larval dietary richness and in local adult nectar resources. The two female morphs determine alternate thermal balance, internal resource allocation and behavioural effects in each species, thus changing the morphs’ time budgets and fitness‐component impacts between the species. In particular, female egg output differences between the morphs appears to reverse between species: alba fecundity is greater than yellow fecundity in C. scudderi, but alba is less than yellow in C. alexandra. 3. These differences are consistent with the large observed differences in alba frequency between the species. Some important questions about the selective regime maintaining a polymorphism here, rather than an alternation of monomorphisms, remain.