There is an inner wax layer composed of strongly oriented long-chain molecules that generally form a monolayer only one molecule thick. The strong orientation provides the waterproof properties of the epicuticle. People think that this is a shellac-like substance that may serve to protect the wax. Terrestrial insects lose water by evaporation from the general body surface - a process called transpiration. The rate of water loss from the surface on any given insect is a function of both wind speed and also of the humidity of air.
Transpiration is relatively independent of body temperature, up to some point.
Water is lost from the body surface at a constant, but rather low, rate through a broad range of temperatures. At some temperature the cuticle reaches a temperature point called the transition point. This point varies from insect to insect, depending upon the chemical composition of the hydrocarbons and waxes in the epicuticle. Insects living in hot, arid habitats tend to have wax layers with higher transition temperatures than do insects living in cooler or more humid habitats. Some insects have two transitions points.