WING-HOOKS OF INSECTS. 349 



The lower edge of the first pair of wings is turned over 

 in a rather stiff fold. The upper edge of the second pair of 

 wings has a row of small, but strong and elastic hooks. When 

 the insect is about to fly, the hooks are hitched into the fold, 

 and so the wings are fastened together. These hooks are 

 shown in the illustration, and the reader will easily see how 

 effective they must be in their operation. An almost exactly 

 similar structure is found in the feathers of birds, and it is by 

 means of these tiny hooks that wings are enabled to present a 

 continuous, light, and elastic surface in the air. 



