INSECTS, 



157 



forms of mouth are but modifications of the same model, 

 adapting it to different functions. The sheath, horny and 

 tubular in the Gnat, soft and muscular in the Fly, is the 

 lower lip ; the piercing lancets in the former are the jaws, 

 which are inconspicuous in the latter. The elegant coiled 

 spire of the Butterfly consists of two tubes, which are the 

 lower jaws, greatly lengthened ; and the labial palpi, 

 stout and hairy, stand up on each side of them : the other 

 essential parts can be detected only by the skill of the 

 anatomist. 



Some of the most interesting of the phenomena which 

 occur in the economy of Insects, are the transformations 

 which they exhibit in their progress of growth ; the 

 changes of their form being frequently so great, that it 

 would be impossible, but for the testimony of experience, 

 to avoid the conclusion that the same insect, in infancy, 

 youth, and adult age, belonged to widely distinct and re- 

 mote orders of existence. We shall enter into some 

 details of this interesting subject in our next chapter. 



