Entomology - with special reference to its biological and economic aspects (1906) (14783555272)

Identifier: entomologywit00fols (find matches)

Title: Entomology : with special reference to its biological and economic aspects

Year: 1906 (1900s)

Authors: Folsom, Justus Watson, 1871-1936

Subjects: Entomology

Publisher: Philadelphia : P. Blakiston's Son

Contributing Library: Robarts - University of Toronto

Digitizing Sponsor: University of Toronto

Text Appearing Before Image:

.Thus a butterfly (P. rapce) makes 9 strokes per second, adragon fly 28, a sphingid moth 72, a bee 190 and a housefly 330. Wing Muscles.—The base of a wing projects into thethoracic cavity and serves for the insertion of the direct mus-cles of flight. Regarding the wing as a lever (Fig. 75, A), ANATOMY AND PHYSIOLOGY 65 with the fulcrum at p, it is easy to understand how the con-traction of muscle c raises the wing and that of muscle d low-ers it. These muscles are shown diagrammatically in Fig.75, B. Besides these, there are certain muscles of flight whichact indirectly upon the wings, by altering the form of thethoracic wall. Thusthe muscle ic (Fig. 75,B) elevates the wingby pulling the tergumtoward the sternum;and the longitudinalmuscle id depresses thewing indirectly byarching the tergum ofthe thorax. Though up anddown movements areall that are necessaryfor the simplest kindof insect flight, theprocess becomes com-plex in proportion tothe efficiencv of the flight. Thus in dragon

Text Appearing After Image:

A, diagram to illustrate the action of the wingmuscles of an insect. B, diagram of wing mus-cles, a, alimentary canal; en, muscle for con-tracting the thorax, to depress the wings; d, de-pressor of wing; e, elevator of wing; ex, musclefor expanding the thorax, to elevate the wings;id, indirect depressor; ie, indirect elevator; /, legmuscle; p, pivot, or fulcrum; s, sternum; t, ter-gum; wg, wing.—After Graber. flies there are ninemuscles to each wing:five depressors, threeelevators and one ad-ductor. Abdomen. — Thechief functions of theabdomen are respiration and reproduction, to v/hich should beadded digestion. The abdomen as a whole has undergone lessdifferentiation than the thorax and presents a simpler and moreprimitive segmentation. Segments.—A typical abdominal segment bears a dorsal6 66 ENTOMOLOGY plate, or tergum, and a ventral plate, or sternum, the two beingconnected by a pair of pleural membranes, which facilitate therespiratory movements of the tergum and sternum. )\I

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1906

University of Toronto

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