Waxes are a very variable class of compounds, mostly carbohydrates, produced by a broad array of plants and animals. In particular, many insects secrete wax from tegumental glands. This then covers the body and, as in many plants, serves as a protection against excess water uptake or water loss at the body surface. Waxes usually have melting points above 40°C, so that they are solid at most ambient temperatures. A given wax has a great many components (Ref. 2: Table 5.1), and within a species it may show considerable geographic variation in its composition.