Wax Blooms in Tenebrionid Beetles of the Namib Desert: Correlations with Environment

Twenty—six species of adult Namib tenebrionid beetles belonging to the tribes Adesmiini and Zophosini have an extracuticular wax bloom covering either part or all of their body surface. These species occur in the dunes, dry river bed, and adjacent gravel plains of the central Namib. The percentage of species possessing a wax bloom increases from the coastal fog desert to the inland hot dry desert. The amount of bloom and its distribution over the integument also increase in a similar manner along the climatic gradient. Despite considerable diversity in coloration and patterns of the wax blooms, the chemical composition of the lipid components showed little variation. Hydrocarbons were the predominant lipid class, with the size of constituent molecules ranging from 19 to 40 carbon atoms. In all species tested, n—alkanes were more abundant than branches alkanes. Odd—numbered carbon chains (e.g., C27, C29, C31) comprised the bulk of the hydrocarbon fractions. The possible functional roles of these blooms in water balance, thermoregulation, predator avoidance, and chemical communication are discussed.