ABSTRACT The production of massive quantities of waxy materials by bees and similar insects has been known for a very long time, but it was not until 1938 that Bergmann showed the existence of smaller quantities of wax in the cuticle of Bombyx. Ramsay (1935) was the first to demonstrate that a greasy material on the surface of the cuticle was responsible for waterproofing the cockroach, and subsequently the work of Wigglesworth (1945) and Beament (1945) produced evidence for believing that the existence of a thin layer of wax in the epicuticle was widespread throughout the insects, and was the chief mechanism for restricting water-loss. It is now known that wax layers are also present in ticks (Lees, 1947) and in many arthropod eggshells (Beament, 1946, 1951, etc.), while Chibnall, Piper, Pollard, Williams & Sahai (1934) have carried out a detailed analysis of beeswax and of the wax of the white pine chermes. These waxes consist of long chain alcohols, paraffins and acids ; the aliphatic chains always appear to be saturated. The similarity of the physicochemical behaviour of cuticular waxes with beeswax, as outlined by Beament (1945), seems to leave little doubt that the minute but essential amounts of wax in typical insect cuticle are composed of the same type of chemical components as those found in beeswax. The range of melting-points of these materials shows that relative changes in the chain length of the component would be sufficient to account for the differences between the specific properties of waxes derived from different species.