176 CATERPILLAR AND IMAGO OF LEPIDOPTERA. 



leaves, in which they excavate galleries ; others envelope them- 

 selves in the membrane of the leaf itself, which they roll together 

 and attach by threads, as seen in Fig. 500, representing the 

 nest of the larva of Tortrix viridana (a small nocturnal moth) 

 which is constructed by rolling the leaves of the Oak. Many 

 construct cases or sheaths, either fixed or portable, by aggluti- 

 nating several substances together, as is done by the larva of 

 of the common Clothes'-Moth ; and there are some that live in 

 societies, dwelling together under a tent of silk, which they spin 

 in common, and which serves to defend them from the incle- 

 mency of the weather. 



770. The imago, or perfect Insect, when it throws off its 

 last envelope and comes forth into the air, of which it is hence- 

 forth to be one of the gayest inhabitants, is not altogether 

 perfect, although capable of very soon becoming so. The wings 

 appear at first very slightly developed, and sometimes even 

 hang loosely at the sides ; and it is not until the animal 

 has injected their tracheae with air, by taking several full 

 inspirations and then forcing it into these passages, that they 

 become expanded so as to serve for flight. From that period 

 the body is supported by them, during by far the largest pro- 

 portion of their active state ; the legs being weak and used only 



VIG. 50!. TORTOISE-SHELL 

 BUTTERFLY JUST EMERGED 

 KKOM THK CHRYSALIS. FIG. 502. DANAIS PLEXIPPA. 



to rest upon, and one pair being sometimes undeveloped (Fig. 

 502). 



77 1 . The Lepidopterous insects are divided into two sections ; 



