Chapter

360 soaks up excess wax. The latter could quickly replace that lost, for example, by surface abrasion. The wax is a complex mixture whose composition varies both among and within species, sometimes over different body regions of the same insect, and in some species seasonally. Generally, long-chain hydrocarbons and fatty acid esters predominate, though varied proportions of alcohols, fatty acids, and sterols may also occur. In some species the mixture has relatively few different components, whereas in others, for example, Musca, more than 100 compounds have been identified (Blomquist and Dillwith, 1985; Jacob et al., 1997). According to Locke (1974), within the wax layer three regions can be distinguished. Adjacent to the cuticulin envelope is a monolayer of tightly packed molecules in liquid form that gives the cuticular surface its high contact angle with water and its resistance to water loss (but see Section 4.2.). Most wax is in the middle layer, which is less ordered and permeates the cement. The outer wax layer, which comprises crystalline wax blooms, is not present in all insects. The innermost layer of the epicuticle, the protein epicuticle, lies beneath the cuticulin envelope. It may be several micrometers thick and like the cuticulin envelope it covers almost all of the surface of the insect. It is absent from tracheoles and parts of some sense organs. It comprises dense, amorphous protein tanned in a manner similar to the protein of the exocuticle (Section 3.3) but contains no chitin.

The cuticulin envelope (about 20 nm thick) extends over the entire body surface and ectodermal invaginations, including the most minute tracheoles, but is absent from specific areas of sense organs and from the tips of certain gland cells. It may be considered the most important layer of the cuticle for the following reasons (Locke, 1974,2001). (1) It is a selectively permeable barrier. During breakdown of the old cuticle, it allows the "activating factor" for the molting gel to move out and the products of cuticular hydrolysis to enter, yet it is impermeable to the enzymes in the molting fluid. It is permeable to waxes (as these are deposited only after the cuticulin layer has formed) and, in some insects, it permits the entry of water. (2) It is inelastic and, therefore, serves as a limiter of growth. (3) It provides the base on which the wax monolayer sits. The nature of the cuticulin envelope will therefore determine whether the wax molecules are oriented with their polar or nonpolar groups facing outward and, therefore, the surface properties of the cuticle. (4) It plays a role in determining the surface pattern of the cuticle. (5) It is resistant to abrasion and helps prevent infection. (6) It is involved in production of physical colors. Despite the importance of the cuticulin envelope, its composition is largely unknown.

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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