The wing pattern polyphenism found in many satyrine
butterflies in regions with wet-dry seasons, has been studied
in a laboratory stock of Bicyclus anynana that was established
from a large number of founders collected in Malawi.
Larvae reared at high (.23°C) or at low (,19°C) temperatures,
produce adults of the wet or dry season form, respectively,(15)
whereas variation in photoperiod has no effect in this
tropical species.(21) The final two larval instars are most
sensitive to ambient temperature,(22) and the alternative
temperature environments in the laboratory broadly match
those that occur in the field in Malawi when cohorts of each
seasonal form are developing.(21) The response of the adult
wing pattern to different rearing environments is more or less
linear with intermediate temperatures giving predominantly
intermediate phenotypes (Fig. 2A). Such phenotypes are
rather infrequent in the wild,(11) where the larvae are likely to
be responding to a complex combination of environmental
factors. Any factor, such as low mean temperature or poor
nutrition, which lengthens larval development enhances the
reduction of the eyespots and medial band on the resulting
adult wings