ABSTRACT
Insects are by far the most numerous animals on Earth, with an estimated 10 individuals alive. The count of about 900,000 known species accounts for more than 80% of all the species of animals on the planet. Given the small body size of insects, the water household is disadvantaged by: a large surface area-to-volume ratio; a limited storage capacity for water, especially for flying insects; and exposure to high temperature and low relative humidity in terrestrial habitats. Thus, a major challenge to terrestrial insects in general is to manage a water household that is threatened primarily by evaporative water loss through the cuticle and the respiratory system. Classically, the cuticle is described as consisting of two main layers: the procuticle and epicuticle. M. Locke, however, has proposed that the thin cuticulin component of the epicuticle is an envelope analogous to that enclosing bacterial cells and that it should be considered an additional main layer.
