WINGET3 INSECTS. 271 



mediate stages of developement. The power of 

 flight is never conferred upon the insect in the 

 earlier periods of its existence: for before its struc- 

 ture can obtain the lightness which fits it for rising 

 in the air, and before it can acquire instruments 

 capable of acting upon so light an element, it has 

 to go through several preparatory changes, some of 

 which are so considerable as to justify the term of 

 metamorphoses, which has been generally given to 

 them.* But transient is the state of perfection in 

 every thing that relates to animal existence. When 

 the insect has, by a slow developement, reached 

 this ultimate elaboration of its organs, its life is 

 hastening to a close ; and the period of its perfect 

 state is generally the shortest of its whole exist- 

 ence. 



The history of the successive stages of the de- 

 velopement of insects opens a highly interesting 

 field of philosophical inquiry. For a certain period 

 of the early life of these animals, the growth of all 

 the parts appears to proceed equably and uni- 

 formly: but at subsequent epochs, some parts 

 acquire a great and sudden increase of size, and 

 others that were in a rudimental condition become 

 highly developed, and constitute what appear to be 

 new forms of organs, although their elements were 

 in existence from a much earlier period. The 

 modifications which the harder and more solid 

 structures of insects exhibit in the progress of these 

 changes, are particularly remarkable, as illustrating 

 the principles on which the developement is con- 



* Transformations quite as remarkable occur in several tribes of 

 animals belonging to other classes : such as those of the Frog among 

 reptiles, and of the Lernopa among parasitic worms. 



