THE Absorption of Water by Woodlice

Abstract

1. Experiments were undertaken to determine the site of water uptake, and the conditions in which it occurs, in Ligia oceanica, Oniscus asellus, Porcellio scaber and Armadillidium vulgare. 2. Besides absorbing water with moist food, all four species were capable of active imbibition of water through both mouth and anus when a free water surface was available. In Ligia oceanica, imbibition occurred largely through the anus, in other species, through the mouth. Absorption through the anus was demonstrated by blocking the mouth by electro-cautery. 3. All species save L. oceanica could imbibe water through the mouth from a damp surface (plaster of Paris) sufficiently rapidly to counteract the effect of transpiration from the integument in air at c. 85 % R.H. No water was absorbed through the anus in these conditions. 4. The results help to resolve certain conflicting statements regarding the distribution of different species in the field. All species are for the most part ‘wet living’, but they differ as regards tolerance of suboptimal conditions.