Water balance in the firebrat, Thermobia domestica (Packard). Exchanges of water with the atmosphere.

Watson (1967) has shown that the synonym Lepismodes iniquilinus Newman has priority over Tliermobia domestica (Packard), but to avoid confusion in the present context the junior synonym as used previously is retained throughout this paper. The ability of Tliermobia to take up water from subsaturated atmospheres down to 45% relative humidity (R.H.) at 21 C. has been demonstrated in an earlier paper (Beament, Noble-Nesbitt & Watson, 1964). The ability to absorb water vapour from subsaturated atmospheres has also been demonstrated in a few other insects, notably in Tenebrio larvae (Buxton, 1930; Mellanby, 1932; Locke, 1964), Chortophaga larvae (Ludwig, 1937), Xenopsylla prepupae (Edney, 1947; Knulle, 1967a) and larvae (Kmille, 1967a) and Arenivaga larvae and adult females (Edney, 1966), and in several acarines, notably in ticks (Lees, 1946-8, 1964; Browning, 1954; Belozerov & Seravin, i960; Camin, 1963; Knulle, 1966) and mites (Knulle, 1962, 1965, 19676; Knulle & Wharton, 1964; Solomon, 1962, 1966; Wharton & Kanungo, 1962; Kanungo, 1963, 1965). This aspect of insect water relations has been reviewed recently in two articles by Beament (1964, 1965). From these other studies have emerged some principles which may be of general application not only to the ability of arthropods to absorb water vapour from subsaturated atmospheres, but also to their ability to restrict transpiratory water losses and to regulate their body-water content. The aim of the present investigation is to examine how far these principles apply in the case of Thermobia. Some of the main results have been reported briefly elsewhere (Noble-Nesbitt, 1968a).