Sources of intraspecific variation in the hostplant seeking behavior of Colias butterflies.

Egg-laying females of the legume-feeding butterfly Colias philodice eriphyle were observed within a high-altitude study site during 1977 and 1978. Average oviposition selectivity showed two pattern sof seasonal variation. First, second brood females laid eggs more frequently after alighting upon hostplants than did first brood females in both years. Second, a consistent decline in post-alighting oviposition probability near the end of the second brood corresponded with a dramatic decrease in the water content of hostplant foliage near the end of the dry summer season. In addition to seasonal variation in oviposition behavior, individual females landed and oviposited upon widely varying sets of legume hostplant species. By sampling hostplant abundances along the flightpaths of observed females, we show that individuals varied in their tendency to land upon different hostplants. Females tended to specialize upon one or two species, at least in the short term, and the pattern of oligophagy for the population as a whole is partly generated by variation in the host-seeking behavior of individual females.