Pupal colour dimorphism in California Battus philenor: pupation sites, environmental control, and diapause linkage

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Abstract
Natural pupation sites and corresponding pupal colour (green or brown) were determined for samples of Battus philenor (L.) from two Californian populations. Larvae pupate off the ground on trees, shrubs and man‐made objects. The vertical distribution of pupation sites and relative frequencies of pupae formed on narrow twigs and broad substrates show interpopulation variability, and seem to be determined by habitat‐specific and possibly behavioural differences among populations. The percentage of‘mismatched’pupae in green leafy environments (brown) is greater than that on wide substrates (green). Heterogeneity in samples of the latter suggest strong but sporadic predation pressure on non‐cryptic pupae in exposed areas. Green and brown substrates generally promoted formation of cryptic green and brown pupae although rearing conditions modified pupal colour response to substrate colour and larval pupation site choice. Warm temperatures and long days increased the production of brown pupae. Short photoperiods increased the tendency of larvae to pupate on narrow twig‐like substrates and to form green pupae. Green pupae show less tendency to diapause than brown pupae. The difference between percentage diapause in the two colour forms increases under conditions favouring progressively more continuous development.