ANIMAL FLIGHT 1 23 



three seconds, which means that it was flying at the rate of 

 nearly 60 miles an hour. 



Dr. Alexander W'elmore has recently determined that the 

 great blue heron flies at the rate of 28 miles an hour, the red- 

 tailed hawk at 22, the flicker at 25, and the raven at 24, so it is 

 evident that the larger dragon-flies have little to fear from birds, 

 though many of the smaller, weaker ones are eaten by them.' 



Such birds as travel at a rate approaching that of the large 

 dragon-flies often become victims of their speed. Being heavy, 

 they cannot turn aside to avoid danger; put a net suddenly 

 in front of them, and into it they go. 



The Esquimaux catch thousands of sea birds annually in 

 this way by intercepting them as they fly along the shore. 

 But the dragon-fly is different. Put a net in front of him and 

 he instantly shoots off sideways, or up or down, or even doubles 

 on his course. He is so light that he has no appreciable mo- 

 mentum and therefore he can twist and turn about in a way 

 quite impossible for any bird. 



There are many different kinds of dragon-flies; all of them 

 eat other insects which they catch upon the wing. They have 

 many different kinds of flight, darting, skimming or soaring 

 about in search of their more or less nimble victims. But the 

 soaring, so-called, of a dragon-fly is a very different thing from 

 the soaring of a bird; at first sight it seems to be the same, 

 but if you watch closely you will see that the dragon-fly keeps 

 his wings in motion almost all the time. 



Dragon-flies have various relatives, Hke ant-lions and lace- 

 winged flies, which, strange to say, are slow and feeble fliers, 

 they are awkward and clumsy in the air and they give you the 

 impression that their wings are too big for them. The dragon- 

 flies and their relatives are the only flying creatures which 

 have two functional pairs of wings acting independently and 

 placed one behind the other as in the original Langley aero- 

 plane. 



The beetles, like the dragon-flies, have two independent pairs 

 of wings, but the wings of the anterior pair are modified in such 



