RESPONSES OF 3 SATURNIID SPECIES TO PAPER BIRCH GROWN UNDER ENRICHED CO2 ATMOSPHERES

1. Interactions between trees and tree-feeding insects are likely to shift under conditions of enriched atmospheric CO2 owing to changes in foliar chemical composition. This study addressed the effects of CO2-mediated changes in leaf chemistry on performance of three silkmoth (Saturniidae) species: cecropia (Hyalophora cecropia), luna (Actias luna) and polyphemus (Antheraea polyphemus polyphemus). 2. Growth under elevated CO2 atmospheres decreased nitrogen concentrations (23%) but tripled starch and doubled condensed tannin concentrations, resulting in a marked increase in foliar carbon:nitrogen ratio. 3. Survival of first stadium larvae was marginally reduced when reared on high CO2 leaves. 4. Development rates were prolonged, growth rates tended to decline, consumption increased and food processing efficiencies decreased for fourth stadium larvae reared on high CO2 leaves. The magnitude of responses varied among species. 5. Overall performance of these saturniid species, at least when feeding on birch, is predicted to decline under atmospheric CO2 conditions anticipated for the next century.