Temperature effects on the growth and dry matter budgets of Malacosoma americanum

Abstract The eastern tent caterpillar ( Malacosoma americanum Fabricius) overwinters as a second-instar pharate larvae. Because the larvae emerge with bud burst they often encounter cold spring temperatures. We tested the hypothesis that M. americanum larvae are metabolically adapted to compensate for the growth-retarding effects of sub-optimal temperatures by determining the growth rate and dry matter budgets for larvae reared at 17,22 or 27°C. Larvae grew more slowly, attained smaller size, had lower gross growth and assimilation efficiencies at lower rearing temperatures. Based on comparison with the effects of rearing temperature on growth performance of other insects, there is no evidence that M. americanum is metabolically adapted for low temperatures. Conversely, the results are consistent with other evidence that M. americanum larvae are behavioural thermal regulators.