The effect of atmospheric humidity on the metabolism of the fasting mealworm ( Tenebrio molitor L., Coleoptera)

Abstract

Previous work has shown that fasting mealworms will live at room tempera­ture for two hundred days, and even at 30°C. they usually live for over a month. During the first two days of starvation the mealworms are restless, and they pass a certain amount of excrement. After this they lie quite still, and pass extremely little excreta. The loss in weight of starving mealworms is different in dry and moist air at one temperature, or in air with the same relative humidity at two temperatures. At 23° C. the mealworms evidently regulate their metabolism, because while they lose weight at different rates in air of various relative humidities, yet they keep the ratio of dry matter to water in their bodies constant (Buxton, 1930). In carrying this work further, I have attempted to find whether the rate at which fasting mealworms evaporate water is proportional at any temperature to the saturation deficiency of the air. Now the fasting mealworm not only evaporates water present in its body at the start of the experiment, but also considerable quantities of water produced by the metabolism of food reserves during starvation. We can estimate the amount of water present in the mealworms at the start of starvation, and can find how much is left at the end of the experiment; the difference represents part of the total water evaporated. But this method does not indicate any metabolic water which is produced and also evaporated during starvation. If one wishes to know the total water evaporated, it can be collected in a stream of air, or else the loss of food reserves must be estimated and the metabolic water produced calculated from these results. I preferred to use the second method, as it is not easy to measure the actual amount of water given off by insects except into dry air.