CH. XXn.] METAMORPHOSES OF INSECTS. 293 



consists in the shedding of the outer skin, without 

 any variation of form taking place, except in a few 

 instances, where an increase is made to the number 

 of legs or to the segments of the body. It is to this 

 kind of transformation, or rather to its pupa state, 

 that Linnaeus gave the name of complete — because 

 at this period it has its various members developed 

 in a greater degree than in any other pupae, and 

 capable of being employed in the economy of the 

 animal. Some authors, including the celebrated 

 Dr. Burmeister, overlooking this circumstance, 

 have considered the term complete to have been 

 applied to the kind of metamorphosis, and, conse- 

 quently, to have been improperly used, the trans- 

 formation being, in fact, the least complete of any 

 undergone by insects. 



It may likewise be considered serviceable to re- 

 mind the reader of the complete difference between 

 insects and vertebrated animals, whence the ne- 

 cessity of these continued moultings will be at 

 once perceived. In the latter, the skeleton to 

 which the muscles are attached is permanent and 

 internal-, but in insects the reverse takes place, the 

 skeleton being external, and, of course, preventing 

 any increase of size, except at the periods of moult- 

 ing. 



To the preceding kind of transformations the 

 domestic bug (Cimex lectularius) appears at first 

 sight to be referrible, from the circumstance of 

 wings not being developed; rudiments of them, 

 however, exist, whence, as well as from other 

 characters, the relationship of this insect to the 

 winged land and water bugs, composing the order 

 Heteroptera, is established ; the latter, although ac- 

 tive and voracious in all their states, and retaining 

 the same general form, possessing in the active 

 pupa state rudiments of wings. These pupae Lin- 

 naeus accordingly termed semi-complete. 



In like manner, if a young frog-hopper {Tetti^ 

 Bb2 



