Hostplant Choice of Checkerspot Larvae: Euphydr Yas Chalcedona, E. Colon, and Hybrids (Lepidoptera: Nymphalidae)

Hostplant preference and hostplant utilization abilities may vary among species, populations (Scriber, 1983; Blau and Feeny, 1983; Singer, 1982, 1983; Holdren and Ehrlich, 1982; Hsiao, 1978; Ehrlich and Murphy, 1981), and individuals (Rausher, 1978; Tabashnik, et al., 1981; Wasserman and Futuyma, 1981; Singer, 1982, 1983). Although such preferences and utilization abilities may be modified by environmental effects such as conditioning (Jermy, et al., 1964; Scriber, 1981; 1982; Grabstein and Scriber, 1982), there is clearly often an obvious genetic component to the patterns of hostplant use observed in nature (e.g., Jaenike and Grimaldi, 1983). The butterfly genus Euphydryas (Nymphalidae) is remarkable for the diverse strategies of hostplant exploitation exhibited by the six species that occur in North America. Euphydryas gilletii, for example, is reported to be virtually monophagous on Lonicera involucrata (Caprifoliaceae), while E. editha, E. chalcedona, and E. anicia are oligophagous, although individual populations may utilize a distinct subset of available hosts (Ehrlich, et al., 1975; Ehrlich and Murphy, 1981; Singer, 1982, 1983). In butterflies, as in many other groups of insects, hostplant utilization is a function of oviposition preference of the female coupled with larval adaptation to the host. In the shift to a new hostplant, change in adult oviposition preference may occur more quickly than larval loss of the ability to utilize ancestral hostplants (Wiklund, 1975; Scriber and Feeny, 1979; Shapiro and Matsuda, 1980; Singer, 1982; Scriber, 1983). Thus adult oviposition behavior may not always reflect larval preference or fitness on a particular hostplant. In a series of elegant experiments with Euphydryas editha, Singer