WINGS AND FLIGHT. 135 



terior wings into cells. The entomological names of 

 those of the anterior wing are given with the illus- 

 tration, as they are frequently used as a basis of 

 classification. 



When, by re-absorption of the contained nutrient 

 fluid, the two facing membranes of each flat pouch 

 are intimately joined, they become the transparent 

 extension of the wing, stretched upon the nervures, 

 which form its stiffening framework. The hollow 

 nervures are never wholly deprived of blood, while 

 through them run large tracheae, which, at the exit of 

 the bee from the cell, aid it in giving that full expansion 

 to its new organs which their office demands. As the 

 eye has left upon it the marks of its method of develop- 

 ment, so the wing gives traces of its origin. The 

 microscope shows that it is dotted over on both sides 

 by small, stiff hairs with an expanded base, while very 

 careful examination reveals that the whole surface is 

 divided, by faint, angular lines, into small areas, which 

 indicate the boundaries of the primary cells, upon the 

 middle of each of which stands a single hair. 



Every wing — be it of bat, bird, or insect — that is 

 capable of acting effectively as an instrument of flight, 

 must, in area, bear some definite proportion to the 

 weight of its possessor. The common bluebottle, a 

 dipterous insect, somewhat less than the honey bee, 

 has its single pair of wings of such a width and so 

 placed that their points are fin. apart when at rest. 

 Had the bee been similarly formed, its wings would 

 have barred its entry to its own cell, which is only -i-in. 

 in diameter ; so that cleaning, filling, and emptying of 

 comb, feeding of brood, and many other essentials, 



