Flight Energetics and Heat Exchange of Gypsy Moths in Relation to Air Temperature

Abstract

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.