Printed in Great Britain SIMULTANEOUS MEASUREMENT OF WATER LOSS AND CARBON DIOXIDE PRODUCTION IN THE CRICKET, ACHETA DOMESTICUS

The relationship between respiration and its contribution to total water loss in arthropods is based almost entirely on correlations obtained from independent plots of gravimetrically-determined transpiration rates and manometrically-detennined gas exchange (Ahearn, 1970; Hadley, 1970). Recently a new system, the 'transpiration monitor ' has been developed to detect the amount of water released by an arthropod into a moving air stream (Hadley, Stuart & Quinlan, 1982). The transpiration monitor not only permits the continuous recording of very small and sporadic losses of moisture, but can be interfaced with either an oxygen or carbon dioxide analyser to provide a simultaneous measure of the arthropod's gas exchange. Thus, peaks that correspond to bursts of moisture can be correlated with concurrent increases in respiratory activity. We report here the application of this system to measure water loss and carbon dioxide production in the cricket, Acheta domesticus, under isothermal conditions and at increasing temperatures. The major components of the transpiration monitor (TM) and their function are summarized below. Air containing no detectable water or carbon dioxide is metere