Mechanisms for the Control of Body Temperature in the Moth, Hyalophora Cecropia

Abstract

ABSTRACT Thoracic temperature in the moth, Hyalophora cecropia, is correlated with gross patterns of behaviour. The animal warms up to a minimum of 34·8 °C body temperature before initiating flight. The rate of warm-up is linear and the duration of the warm-up period increases with decreasing air temperature. Thoracic temperature at the initiation of flight and during maintained flight remain constant at any given air temperature, however, decreases 0·25 °C per °C gradient as air temperature is decreased. Distribution of the maximum and minimum thoracic temperatures during active periods indicate that the animal maintains its body temperature within a favourable range. The animal uses behavioural mechanisms to maintain the thoracic temperature within this range when the body temperature reaches the limits, 33·4 and 37·8 °C. The minimum thoracic temperature for flight (34·8 °C) and the shade-seeking temperature (38·5 °C) correspond closely to the limits predicted from the maximumminimum distribution of thoracic temperatures. The theoretical minimum and maximum rates of oxygen consumption were calculated from cooling curves and warm-up curves. Both rates increase when the gradient between body temperature and air temperature increases (air temperature is lowered, body temperature remains relatively constant). Directly measured rates of oxygen consumption in flying animals increase as air temperature decreases. These values fall within the calculated maximum and minimum in all cases. Oxygen consumption measured in torpid animals indicates a normal poikilo-thermic response, increasing with increased air temperature. The Q10 for this response is 2·25 over the range 20–30 °C. A model for the regulation of body temperature in active moths is discussed.