396 INSECT TRANSFORMATIONS. 



former opinions on the flight of insects ; yet it might 

 have been supposed, that in writing so voluminously 

 on the subject, he had left no point uninvestigated. 

 Nothing, however, can be more praiseworthy than 

 the candour (not very common in such cases) with 

 which Chabrier corrects his own mistake. 



In the two-winged flies (Diptera) Chabrier de- 

 scribes two sets of muscular ribbons for putting the 

 wings in play — the dorsal, placed lengthwise, and 

 used to lower the wings, and the sterno-dorsai, placed 

 obliquely across these for raising the wings. In the 

 dragon-flies (LibeUulina), again, the disposition is 

 somewhat different, the sterno-dorsal muscles being 

 placed intermediate, while another set of powerful 

 muscles, called pectoral, are placed lengthwise, and 

 are inserted immediately into the wings. In his first 

 work, our author thought these muscles acted sepa- 

 rately, but he now says they act in concert ; and he 

 is not now inclined to ascribe, as he at first did, so 

 much influence to the air in the interior of the body, 

 nor to the spring of the harder parts of the back 

 and breast. " Certainly," he adds, " the elasticity of 

 these parts, and the re-action of the interior air have 

 their use : the fluid, particularly, contained in their 

 numerous vesicles is, perhaps, very light, and con- 

 tributes to reduce the specific gravity of the insect. 

 Besides, by enveloping the interior organs, it ap- 

 pears to me intended to protect these against the vio- 

 lent motions of flight, and to contribute to the ex- 

 pansion of the chest, dilating immediately after being 

 compressed by the contraction of the muscles in the 

 act of raising the wings."* 



It will appear, from this brief abstract, that the 

 subject is not a little interesting; yet it is not so easy 

 to throw it into a form likely to be understood by a 

 general reader. Flying with wings, however, is a 



•' M. Chabrier In Ann. des Soc. Nat., Avril, 1829, p. 505. 



