320 THE L1FK OF AN INSECT. 



are the wings expanded ? by what means do they, 

 from being thick, soft, and moist, become thin, 

 hard, and dry ? It is to be regretted that this 

 inquiry cannot be answered with that satisfactory 

 certainty which it deserves. It is very difficult to 

 catch the insects in which the expansion of the 

 wings is best observed at the right moment ; and 

 even then it is extremely difficult to say whether 

 one cause more than another may contribute to 

 this phenomenon. The following explanation of 

 it is given by Messrs. Kirby and Spence, whose 

 general accuracy on such subjects is well known. 

 " As soon as the insect is disclosed, a fluid enters 

 the tubes or nervures, and being impelled into 

 their minutest ramifications, necessarily expands 

 their folds ; for the nervures themselves are folded, 

 and as they gradually extend in length with them, 

 the moist membranes attached to them are also 

 unfolded and extended. In proportion as this 

 takes place, the expanding membranes approach 

 each other, and at last, being dried by the action 

 of the atmosphere, become one. To promote this 

 motion of the fluid seems the object of the agi- 

 tations which, in many instances, the animal from 

 time to time gives to its unexpanded wings. That 



