iv.] METAMORPHOSES OF INSECTS. 73 



change than any relating to the mouth, we are apt 

 to associate with it the existence of a pupa-state : 

 but the case of the Orthoptera (grasshoppers, &c.) is 

 sufficient proof that the development of wings is per- 

 fectly compatible with permanent activity ; the necess- 

 ity for prolonged rest is in reality much more inti- 

 mately connected with the change in the constitution 

 of the mouth, although in many cases, no doubt, this 

 is accompanied by changes in the legs, and in the 

 internal organization. An originally mandibulate 

 mouth, however, like that of a beetle, could not, I 

 think, have been directly modified into a suctorial 

 organ like that of a butterfly or a gnat, because the 

 intermediate stages would necessarily be injurious. 

 Neither, on the other hand, for the same reasons, 

 could the mouth of the Hemiptera be modified into 

 a mandibulate type like that of the Coleoptera. But 

 in Campodca and the Collembola we have a type of 

 animal closely resembling certain larvae which occur 

 both in the mandibulate and suctorial series of in- 

 sects, possessing a mouth neither distinctly mandi- 

 bulate nor distinctly suctorial, but constituted on a 

 peculiar type, capable of modification in either direc- 

 tion by gradual change, without loss of utility. 



In discussing this subject, it is necessary also to 

 take into consideration the nature and origin of wings. 

 Whence are they derived ? why are there normally 

 two pairs ? and why are they attached to the meso- 

 and meta-thorax ? These questions are as difficult 

 as they are interesting. It has been suggested, and 

 I think with justice, that the wings of insects ori- 

 ginally served for aquatic and respiratory purposes. 



