THE TRANSITION PHENOMENON IN RELATION TO THE PENETRATION OF WATER THROUGH THE CUTICLE OF AN INSECT, CENOCORIXA EXPLETA (HUNGERFORD)

Abstract

The evaporation rates and cuticle temperatures of adult Cenocorixa expleta were measured in a stream of dry air at temperatures ranging from 20 °C to 45 °C. These insects have a transition point which varies with individuals; it lies between 30 °C and 35 °C of ambient dry air, or 28.5 °C and 32.8 °C of cuticle temperature. Thus composite evaporation/temperature curves do not reveal this phenomenon. If transition is caused by high temperature air, it is reversible; however, waterproofing is restored at a temperature which is lower than that of transition.Immersion of insects in water or surfactant solutions at 30 °C to 35 °C also causes transition. In either case it is irreversible, possibly owing to the removal of the epicuticular wax.Theoretical and ecological implications are discussed.