Image from page 80 of "Entomology : with special reference to its biological and economic aspects" (1906)
Authors: Folsom, Justus Watson, 1871-1936
Publisher: Philadelphia : P. Blakiston's Son
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto
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Text Appearing Before Image:
Wing of Lcltinotarsa dccemlincata. A, spread; B, folded; a, costal joint; ah,articular head; an, anterior system of veins; b, transverse vein; c, cotyla; d, joint;m, middle system of veins; p, posterior system of veins.—After Tower. ous sclerite of the thorax, which stops the further movementof the cotyla medianward, and as the wing swings farther backthe middle system of veins (///) is pushed outward and ante-riorly. This motion, combined with the backward movementof the wing as a whole, produces the folding- of the distal endof the wing. There are no traces of muscles or elastic liga-ments in the wing which could aid in the folding. Mechanics of Flight.—The mechanism of insect flight ismuch less complex than one might anticipate. Indeed, owingto the structure of the wing itself, simple up and down move-ments are sufticient for the simplest kind of flight. During ANATOMY AND PHYSIOLOGY 63 Fig. 72,.
Text Appearing After Image:
Trajectory of the wing of aninsect. oscillation, the plane of the wing changes, as may be demon-strated by holding a detached wing by its base and blowing atright angles to its surface; the membrane of the wing then yieldsto the pressure of the air while the rigid anterior margin doesnot, to any great extent. Similarly, as the wing moves down-ward the membrane is inclined upward by the resistance of theair, and as the wing moves upward the membrane bends down-ward. Therefore, by becoming deflected, the wing encountersa certain amount of resistance frombehind, which is suflicient to propelthe insect. The faster the wingsvibrate, the greater the deflection.the greater the resistance from be-hind, and the faster the flight of theinsect. The path traced in the air l)ya rapidly vibrating wing may bedetermined by fastening a bit of gold leaf to the tip of thewing and allowing the insect—a wasp, for example—to vibrateits wings in the sunlight, against a dark background. Underthese condit
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