Entomology : with special reference to its biological and economic aspects . cess of flight, and obtained at first twenty, and later onehundred and ten, successive photographs per second of a beein flight. As the wings were vibrating 190 times per second,however, the images evidently represented isolated and notconsecutive phases of wing movement. Nevertheless, theimages could be interpreted \\ithout difticulty, in the light ofthe results obtained by other methods. At length he obtainedsharp but isolated images of vibrating wings with an exposureof only 1/25,000 of a second. The frequency of w
Entomology : with special reference to its biological and economic aspects . cess of flight, and obtained at first twenty, and later onehundred and ten, successive photographs per second of a beein flight. As the wings were vibrating 190 times per second,however, the images evidently represented isolated and notconsecutive phases of wing movement. Nevertheless, theimages could be interpreted \\ithout difticulty, in the light ofthe results obtained by other methods. At length he obtainedsharp but isolated images of vibrating wings with an exposureof only 1/25,000 of a second. The frequency of wing vibration may be ascertained fromthe note made by the wing—if it vibrates rapidly enough to 64 ENTOMOLOGY make one; and, in any case, may be determined graphically bymeans of a kymograph, which, in one of its forms consists ofa cylinder covered with smoked paper and revolved by clock-work at a uniform rate. The insect is held in such a positionthat each stroke of the wing- makes a record on the smokedpaper, as in Fig. 74. Comparing this record with one made Fig. Records of wing vibration. A, mosquito, Anopheles. Above is the wing recordand below is the record of a tuning fork which vibrated times per second. B,wasp, Polistcs. Tlie tuning fork in this instance had a vibration frequency of on the same paper by a tuning fork of known vibration period,the frequency of wing vibration can be determined with greataccuracy. As the wing moves in the arc of a circle, the radiusof which is the length of the wing, the extreme tip of the wingrecords only a short mark; if, however, the wing is pressedagainst the smoked cylinder, a large part of the figure 8 trajec-tory may be obtained, as in Fig. 74, B. The wings of the twosides move synchronously, as Marey found. The smaller the wings are, the more rapidly they 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
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1
