The coevolution of Euphydryas chalcedona butterflies and their larval host plants : II. Maternal and host plant effects on larval growth, development, and food-use efficiency.

The effects of foodplant species and maternal food type on larval growth, development, and digestive parameters were examined for larvae from an oligophagous colony of Euphydryas chalcedona butterflies. Broods of larvae from areas containing two different foodplants, Diplacus aurantiacus and Scrophularia californica, were divided. One group was fed their "native" host and their siblings were fed the other species. Growth and digestion parameters were measured from hatching until larvae entered diapause.Larvae that fed on Scrophularia grew faster and larger, and suffered lower mortality than their siblings that fed on Diplacus. Growth and digestion indices for larvae from the two maternal-host types did not indicate genetically mediated differences in food-use efficiency; Scrophularia was more digestible than Diplacus to all larvae. Larvae showed a strong feeding preference for Scrophularia, regardless of previous food or presumed maternal-host type. However, larvae that had been reared on Diplacus ate more Diplacus than larvae that had been reared on Scrophularia. In addition, all larvae were capable of increasing gut pH when fed Diplacus. Thus, the effect of previous feeding experience on host utilization and preference by larvae was more significant than the effect of the presumed maternal-host type.