. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MECHANICS OF FLIGHT IN DIPTERA 203 nomenclature by morphologists, the term scutellar lever is used here as it best de- scribes the action of this part of the notum. The scutellar lever by its simple rotary action and strong construction is designed to transmit the power of the indirect muscles to the wing root sclerites. In the downstroke the longitudinal muscle moves the hinge points (i, Figs. 1 and 2) for- ward, closing the lateral vertical clefts (n-o, Fig. 1A), while the upward movement of the notum opens the cleft (k-f)
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MECHANICS OF FLIGHT IN DIPTERA 203 nomenclature by morphologists, the term scutellar lever is used here as it best de- scribes the action of this part of the notum. The scutellar lever by its simple rotary action and strong construction is designed to transmit the power of the indirect muscles to the wing root sclerites. In the downstroke the longitudinal muscle moves the hinge points (i, Figs. 1 and 2) for- ward, closing the lateral vertical clefts (n-o, Fig. 1A), while the upward movement of the notum opens the cleft (k-f). Mihalyi (1935/36) first explained the impor- tance of these clefts in allowing proper movement of the thoracic parts. At the same time there is also a lateral expansion of the notum, especially at f (Figs. 1 and 2). The notum rides up and back as the hinge points (i) move forward; the scutel- lum tips down, and the lever arms move upward. If there is a definite fixed axis on which this rotation occurs, it must lie between points (i) and (1) for (i) moves (1) moves back. The part played by these structures in the upstroke is as follows. The vertical muscles reverse the rotation produced by the longitudinal muscle. In this action the whole notum anterior to the scutoscutellar suture serves as a lever with fulcrum at j-k (Fig. 1A) and moves the scutellar lever down by action at the attachment. /i FIGURE 2. Horizontal section through the notum. Structures labeled as in Figure 1 with the following additions : v, prescutal ridge; w, chitinous supporting structure; x, anterior hardened plate; 1, first dorsoventral muscles; 2, second dorsoventral muscles; 3, oblique dorsal muscles; 4, tergal remoter muscles; 5, longitudinal muscles. line (1-h-m, Fig. 1A). The first dorsoventral muscles shorten very little and move the lever at considerable mechanical disadvantage. They are effective, however, in producing lateral expansion at point f and stiffening the thorax. The second
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
