Thermal ecology, behavior, and growth of gypsy moth and eastern tent caterpillars

Eastern tent caterpillars (Malacosoma americanum) are behavioral thermoregulators while gypsy moth caterpillars (Lymantria dispar) are thermal conformers. Differences in thermal ecology can be related to differences in the environments these species encounter. Temperature sensitivity of growth rates differs in a predictable manner; the growth rates of gypsy moth caterpillars are temperature independent at ecologically relevant temperatures of 25@?-30@?C, and the growth of the tent caterpillars is very temperature dependent. Growth rates of tent caterpillars in the field are greater than that expected for the average ambient temperature of 15@?, and closely approximate growth in the laboratory at 25@?, near the average T"b exhibited in the field. The higher growth rates are a result of the tent caterpillars' elevated body temperatures. These data are used to develop hypotheses for the evolution of caterpillar thermal responses.