358 



INSECTA. 



formed, and retains the same appearance during the whole period of the 

 existence of the insect in its larva state ; but underneath this cuticle, 

 and consequently concealed from observation, the growth of the living 

 dermis still goes on, and important organs begin to appear, which had 

 no existence when the last larva-investment was secreted. The wings 

 have sprouted as it 



were from the shoul- Fig. 181. 



ders, and already have 

 attained to a certain 

 growth ; the whole in- 

 tegument of the larva 

 becomes useless, and a 

 new one is wanted; 

 the process already de- 

 scribed is repeated, 

 the old cuticle becomes 

 detached from the sur- 

 face of the body, and 

 the cutis begins to se- 

 crete for itself a new 

 covering moulded upon 

 its own shape. The 

 newly-formed wings, 

 therefore, and other 

 newly- developed pro- 

 cesses of the dermis, 

 secrete horny coverings 

 for themselves in the 

 same manner as other 

 parts of the surface of 

 the body ; and thus, 

 when the insect leaves 

 its old skin, and once 

 more escapes from con- 

 finement, it presents to 

 view the wing-cases 

 which distinguish the 

 pupa. 



(924.) Whatever may 

 be the form of the pupa, 

 its covering is secreted 

 in a similar way ; it is 

 the living and vascular skin which, though concealed, continually grows 

 more perfect in its parts ; and the cases secreted by it at distant intervals 

 correspond in shape with the different phases of its development. 



Metamorphosis of the Dragon-fly. A, B, eseape of the imago 

 from its pupa-case; C, expansion of the, as yet, undeve- 

 loped wings. 



