The Utilisation of metabolic Water in Insects

Abstract

(1) Three insects,Tribolium confusum, Ephestia kuehniellaandDermestes vulpinus, have been grown at several humidities and the following factors have been determined: length of larval period; water content of food and of the freshly formed pupae; wet and dry weight of pupae and wet and dry weight of food consumed during larval development. The “net utilisation” of the food has been calculated as the ratio of dry weight of food eaten per larva to dry weight of pupa.(2) At lower humidities more food is eaten to produce a given unit of body weight. The length of the larval period increases and the weight of the pupae decreases.(3) More food is eaten at low humidities, because part of the food is utilised as water. As a consequence of this, the larva grows more slowly and its final size is smaller. It is shown forDermestesat 30 per cent. andEphestiaat 1 per cent. R.H. that less than 32·9 and 7·6 per cent. of the water in the pupae can be derived from water ingested with the food.