Water balance inTenebrio molitor, L. Larvae; the effect of atmospheric water absorption

Abstract

Fasting mealworms gain weight in 98 and 92, but not in 85% R.H. at rates which increase with humidity and animal size above a threshold of 88.2%. Weight gains are associated with substantial increases in body water content and considerable haemolymph dilution. Blocking the anus eliminates weight gains confirming the rectum as the probable site of atmospheric absorption. No absorption was observed in animals five days before and one day following ecdysis. Fasting mealworms lack adequate means of regulating atmospheric absorption during prolonged exposure to high humidities. Initial absorption in fasting animals permits accelerated growth when they are subsequently fed. Calculations estimate that a net gain of water from the food only occurs in humidities above 70%. Atmospheric absorption is about 1.5 times faster than net gain from the food at 98% R.H. and almost three times as fast in 92%.