Costal

veins Claval furrow

4.5. A generalized wing, indicating major vein systems and the terminology used in this book.

veins Claval furrow

4.5. A generalized wing, indicating major vein systems and the terminology used in this book.

on various modifications of the Comstock-Needham system (e.g., Comstock and Needham, 1898, 1899; Kukalova-Peck, 1991). Here, we adopted the system that is most similar to that espoused by Wootton (1979) (Figure 4.5). Major longitudinal veins typically have major branches, each given names, and are indicated by uppercase letters with their branches indicated by subscripts. Crossveins are small, secondary veins running between the longitudinal veins and are generally indicated by lowercase letters; a hyphen separates the anterior-posterior longitudinal veins that they connect (e.g., sc-r = a crossvein from the subcosta to radius). The archedic-tyon is an irregular network of many short crossveins between the longitudinal veins and is believed to be the primitive condition for winged insects. The major, longitudinal vein systems in insects follow (refer also to the section on pteralia later in this chapter).

Costa (C+): this vein is usually on or just behind the anterior wing margin (if there is a small membranous area anterior to C, then it is typically called the precostal area). The costa can meet at its base a small sclerite called the humeral plate (see the discussion of pteralia later in this chapter).

Subcosta (Sc-): this vein sometimes has two branches and contacts the first axillary sclerite at the wing base.

Radius (R): the radius branches into two components, the true radius (R+) and the radial sector (Rs-). The base of the radius contacts the second axillary sclerite. Although it is a major longitudinal vein, Rs- does not extend directly to a sclerite at the base of the wing and instead originates directly as a branch from the radius; it is therefore considered part of the radial system. Rs-forks a variable number of times into veins R2-5, sometimes called Rs1-4. The original stem of Rs is concave, but its branches can sometimes alternate between convex and concave, though typically they are all concave.

Media (M): the base of the media contacts the distal end of the medial plate. Typically the media has two major branches (which will also fork) called the media anterior (MA+) and the media posterior (MP-). MA+ typically forks to form two branches (M1-2 or MA1-2) as does MP- (M3-4 or MP1-2). MP- can have more branches at times.

Cubitus (Cu): this is typically a three-branched vein that contacts the distal medial plate. Like the median, there is an anterior cubitus (CuA+) and a posterior cubitus (CuP-). CuA+ typically branches.

Anal veins (A+): the number of anal veins (called vannal by Snodgrass and earlier authors) is variable, and the veins are usually unbranched.

As noted, these veins contact pteralic sclerites that form the articulation at the base of the wing. The principal components of the pteralia are the axillary sclerites, tegula, humeral plate, and in Neoptera the medial plates. Typically there are three axillary sclerites that are positioned in different membranes of the wing (Figure 4.6). The first axillary sclerite lies in the dorsal membrane and articulates at its base with the anterior notal wing process and distally with vein Sc and the second axillary sclerite. The second axillary sclerite runs in both dorsal and ventral membranes and articulates ventrally with the pleural wing process and distally with vein R. It also attaches to the third axillary sclerite. The third axillary scle-rite lies in the dorsal membrane and articulates with the posterior notal wing process and the anal veins. In the Hymenoptera and Orthoptera there is sometimes a fourth axillary sclerite (perhaps derived posteriorly from the third) that lies between the third axillary sclerite and the posterior notal wing process. The third axillary sclerite is Y-shaped with a flexor muscle inserting in the crutch of the Y, the other end of the muscle originating on the inner surface of the pleuron. When this muscle flexes, the wings fold over the abdomen

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