Gypsy moths elevate thoracic temperature (Tth) during flight by endogenous heat production but do not regulate it. Thoracic temperature of moths in free, near-hovering flights exceeded air temperature by approximately 6–7 °C at all Tα's between 17 and 32 °C. Mean rates of mass specific oxygen consumption varied between 40 and 47 ml O2 (g·h)−1 and were not correlated with air temperature. Wing-beat frequency increased from 27 to 33 (s)−1 between air temperatures of 18 and 35 °C. Thoracic heating and cooling constants are similar in live and dead moths, and removal of thoracic scales increases heating constants by about 12%. Preflight warm-up occurs at low Tα's but the moths are capable of immediate, controlled flight at Tα's above 22 °C. Relatively low levels of heat production by the flight muscles are a consequence of low power requirements associated with the flight morphology of gypsy moths. Calculated rates of thoracic and respiratory heat loss of free-flying moths are slightly lower than values of heat production.

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