344 THE MECHANICAL FUNCTIONS. 



§ 9. Flight of Insects. 



If the excellence of a mechanic art be mea- 

 sured by the difficulties to be surmounted in the 

 attainment of its object, none surely would rank 

 higher than that which has accomplished the 

 flight of a living animal. No human skill has 

 yet contrived the construction of an automaton, 

 capable, by the operation of an internal force, of 

 sustaining itself in the air, in opposition to gra- 

 vity, for even a few minutes ; and far less of 

 performing in that element the evolutions which 

 we daily witness even in the lowest of the insect 

 tribes. To the ultimate attainment of this fa- 

 culty it would appear that all the transforma- 

 tions they undergo in external appearance, and 

 all the dev elopements of their internal me- 

 chanism, are expressly directed. Wings are 

 added to the frame only in the last stage of its 

 completion ; after it has disencumbered itself of 

 every ponderous material that could be spared, 

 after it has been condensed into a small com- 

 pass, and after it has been perforated in all 

 directions by air-tubes, giving lightness and 

 buoyancy to every part. Curiously folded up 

 in the pupa, the wings there attain their full 

 dimensions, ready to expand whenever the ban- 

 dages that surround them are removed. No 



