Forest tent caterpillars are ectotherms so they rely on sources of heat from the environment to raise their body temperatures. In order to do this, they bask together and benefit from group thermoregulation. Elevating body temperature is essential in increasing metabolic rates for movement and food processing, so proper thermoregulation leads to an increased rate of development. This is very important for "M. distria" caterpillars, which rely on fast growth in spite of low environmental temperatures to benefit from the high food quality and the smaller predation risk in the spring. Thus, it is an adaptive advantage to bask in groups. However, as caterpillars grow, thermoregulatory needs decrease and the benefit of group living is gradually overridden by other factors such as food competition.