FLIGHT OF INSECTS. 



187 



loops usually predominates over the other ; it is generally the 

 lower one which increases while the upper diminishes. Indeed, 

 by a still greater opening, the figure is occasionally trans- 

 formed into an irregular ellipse, at the extremity of which MO 

 can recognise a vestige of the second loop. 



Fio. 7 



wii ., 

 beam. 



71. Appearance of a wasp, the extremity of each of w 

 ings has been gilded. 'Jhc insect is supposed to be place 



who ;o liwg -T 

 :d ill a sun- 



We thought that we had been the first to point out the form 

 of the trajectory of the wing of the insect, but Dr. J. B. Petti- 

 grew, an English author, informs us th-it he had already 

 mentioned this figure of 8 appearance described by the wing, 

 and had represented it in the plates of his work.* It will 

 be seen presently that, notwithstanding this apparent agree- 

 ment, our theory and that of Dr. Pettigrew differ materially 

 from each other. 



Changes of the plane of the iriiifj. The luminous appearance 

 given during flight by the gilded wing of an insect, shows 



* On the Mechanical Appliances by which Flight is Maintained in the 

 Animal Kingdom. Transact, of Linnean Society, 1S67,. p. 233. 



