236 THE HAUNTS OF LIFE 



gave some hints to the early makers of aero- 

 planes, are not only very swift, but have an 

 astonishing power of changing their direction 

 instantaneously. This is well suited for catch- 

 ing other insects on the wing. Another re- 

 markable feature in the flight of dragon-flies 

 is that when they pass from a sunny to a 

 shaded part they often begin at once to prac- 

 tise that mysterious kind of flight called 

 "soaring," so well seen in vultures circling in 

 mid-air; that is to say, they continue moving, 

 but without any visible wing-strokes. 



There is no end to the interesting peculiari- 

 ties of flight in different orders of insects. 

 Bees and their relatives have microscopic 

 hooklets on the front edge of the hind-wings 

 which fix on to a bar on the hind edge of the 

 fore-wings, so .that the two wings on each side 

 act as one. In moths and butterflies the same 

 result comes about less perfectly. Beetles 

 spread out their heavy fore-wings too heavy 

 to be used in striking the air and clamp 

 them at right angles to the length of the body, 

 so that they serve as vol-planes when the 

 lightly built hind-wings strike the air. In 

 two-winged flies the hind-wings are turned 

 into rapidly quivering "poisers," each like a 



