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 practise 

 that mysterious kind of flight called " soaring," 

 so well seen in vultures circling in mid-air ; 

 that is to say, they continue moving, but with- 

 out any visible wing-strokes. 



There is no end to the interesting peculiarities 

 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 stalked half dumb-bell; 



