Chapter

80 basal lamina) and its lumen, being an extension of the hemocoel, contains tracheae, nerves, and hemolymph. As the wing develops, the dorsal and ventral integumental layers become closely apposed over most of their area forming the wing membrane. The remaining areas form channels, the future veins, in which the nerves and tracheae may occur. The cuticle surrounding the veins becomes thickened to provide strength and rigidity to the wing. Hairs of two types may occur on the wings: microtrichia, which are small and irregularly scattered, and macrotrichia, which are larger, socketed, and may be restricted to veins. The scales of Lepidoptera and Trichoptera are highly modified macrotrichia. For a detailed review of wing morphology, see Wootton (1992).

It must be assumed that the extremely varied arrangement of veins found among the insect orders is derived from a primitive common pattern, the ground plan or archetype venation. Details of the latter will never be known with certainty because even the earliest fossilized wings had a highly complex venation. In order to develop a basic plan of wing venation, it is necessary to compare (and homologize) not only the veins, but also flexion lines (lines along which a wing creases during flight), fold lines (where wings crease during folding), and wing areas (areas delimited by specific veins and/or lines) (Wootton, 1979). Given the diversity of wings of insects, both fossil and extant, it is not surprising that authors have sometimes reached quite different conclusions with respect to the homologies of veins (compare Figures 2.2 and 3.26). This is unfortunate given the enormous importance of wing venation in phylogenetic and taxonomic studies.

The usual method of determining homology is direct comparison of the position and form of veins. In addition, there are other, more subtle features with which to assess potential homologies (Ragge, 1955; Hamilton, 1972a; Lawrence et al., 1991). Thus, certain veins are always associated with particular axillary sclerites. Tillyard (1918) made use of the fact

FIGURE 3.26. Basicscheme of wing venation, flexion lines andfoldinglines. (A) Fore wing or hind wing without vannus; and (B) vannal area of hind wing. [After R. J. Wootton, 1979, Function, homology and terminology in insect wings, Syst. Entomol. 4:81-93. By permission of the Royal Entomological Society.]

FIGURE 3.26. Basicscheme of wing venation, flexion lines andfoldinglines. (A) Fore wing or hind wing without vannus; and (B) vannal area of hind wing. [After R. J. Wootton, 1979, Function, homology and terminology in insect wings, Syst. Entomol. 4:81-93. By permission of the Royal Entomological Society.]

that some veins have associated with them a row of macrotrichia. In many wings this row persists even when the original vein has disappeared. The widely used Comstock-Needham system of wing venation was based on the assumption that tracheae are always present in particular veins and that the pattern of tracheae develops in a characteristic manner and thereby determines the venational pattern (Comstock, 1918). In fact, the lacunae from which veins arise develop as hemolymph channels and it is only after veins have formed that tracheae and nerves extend into them. In addition, tracheal patterns may differ, for example, between pupal and adult instars, according to different functional needs. Other authors have based their studies of vein homology on wing fluting, the alternation of concave and convex veins. This approach is of limited use, however, and is not applicable to branched vein systems where fluting is practically non-existent, or to wings that are secondarily fluted (Hamilton, 1972a).

Wootton (1979) made a major contribution toward resolution of the confusion over the nomenclature of veins and other wing components. His scheme, presented in Figure 3.26, includes the following longitudinal veins (from anterior to posterior): costa, subcosta, radius, radial sector, anterior media, posterior media, anterior cubitus, posterior cubitus, and anals (of which there may be several). Any of these veins may be branched, though the costa and posterior cubitus rarely are because the former is at the leading edge of the wing while the latter is associated with the claval furrow. In wings with a jugum (see below), jugal vein(s) may occur. The major flexion lines are the median flexion line, which originates just behind the media and runs outward just behind the radial sector, and the claval furrow, which lies along the posterior cubitus (Figure 3.27). Though fold lines may be transverse, as in the hind wings of beetles and earwigs, they are normally radial to the base of the wing, allowing adjacent sections of a wing to be folded over or under each other. The commonest fold line is the jugal fold, situated just behind the third anal vein. In hind wings with an

FIGURE 3.27. Diagram showing the major areas, margins and angles of a generalized wing. (A) Fore wing or hind wing without vannus; and (B) vannal area of hind wing [Partly after R. J. Wootton, 1979, Function, homology and terminology in insect wings, Syst. Entomol. 4:81-93. By permission of the Royal Entomological Society.]

FIGURE 3.27. Diagram showing the major areas, margins and angles of a generalized wing. (A) Fore wing or hind wing without vannus; and (B) vannal area of hind wing [Partly after R. J. Wootton, 1979, Function, homology and terminology in insect wings, Syst. Entomol. 4:81-93. By permission of the Royal Entomological Society.]

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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