MOTIONS OF INSECTS. 357 



like a hawk, is so rapid as not to be perceptible. Wlien 

 the crane-fly {Tipula olcracea) is upon the wing, its fore- 

 legs are placed horizontally, pointing forwards, and the 

 four hind ones stretched out in an opposite direction, the 

 one forming the prow and the other the stern of the 

 vessel, in its voyage through the ocean of air. The legs 

 of another insect of this tribe {Hirtaa Maixi) all point 

 towards the anus in flight, the long anterior pair forming 

 an acute angle with the body : — thus, perhaps, it can 

 better cut the air. 



I have often been amused in my walks with the motions 

 of the hornet-fly (Asihcs crabronifoi'mis)^ belonging to 

 the second division just mentioned. This insect is cai- 

 nivorous, living upon small flies. When you are taking 

 your rambles, you may often observe it alight just before 

 you ; — as soon as you come up, it flies a little further, 

 and will thus be your avant-courier for the whole length 

 of a long field. This usually takes place, I seem to have 

 observed, when a path lies under a hedge ; and perhaps 

 the object of this manoeuvre may be the capture of prey. 

 Your motions may drive a number of insects before you, 

 and so be instrumental in supplying it with a meal. 

 Other species of the genus have the same habit. 



The aerial progress of the fly tribes, including the 

 gad-flies {CEstridcc) -, horse-flies {Tabanidce) \ carrion- 

 flies {Muscidce), and many other genera — which constitute 

 the heavy horse amongst our two-M'inged fliers — is won- 

 derfully rapid, and usually in a direct line. An anony- 

 mous observer in Nicholson's Journal ^ calculates that, in 

 its ordinary flight, the common house-fly [Musca domes- 

 tica) makes with its wings about 600 strokes, which 

 " 4to. iii. 36. 



