STATES, OF INSECTS. 293 



particularly of the wings, and the perfect coming forth of 

 the colours and spots, as the sun gave vigour to it, was a 

 most interesting spectacle. At first it was unable to ele- 

 vate or even move its wings ; but in proportion as the 

 aerial or other fluid was forced by the motions of its trunk 

 into their nervures, their numerous corrugations and folds 

 gradually yielded to the action, till they had gained their 

 greatest extent, and the film between all the nervures be- 

 came tense. The ocelli, and spots and bars, which ap- 

 peared at first as but germes or rudiments of what they 

 were to be, grew with the growing wing, and shone forth 

 upon its complete expansion in full magnitude and 

 beauty. 



To understand more clearly the cause of this rapid 

 expansion and development of the wings, I have before 

 explained to you that these organs, though often exceed- 

 ingly thin, are always composed of two membranes, hav- 

 ing most commonly a number of hollow vessels, miscalled 

 nerves, running between them a . These tubes, which, 

 after the French Entomologists, I would name nervures, 

 contribute as well to the development of the wings, as to 

 their subsequent tension. In the pupa, and commonly 

 afterwards, the two membranes composing the organs in 

 question do not touch each other's inner surface, as they 

 afterwards do : there is consequently a space between 

 them ; and being moist, and corrugated into a vast num- 

 ber of folds like those of a fan, but transverse as well as 

 longitudinal, and so minute as to be imperceptible to the 

 naked eye, the wings appear much thicker than in the 

 end. Now as soon as the insect is disclosed, a fluid enters 



1 See above. Vol. II. p. 346. 



