362 MOTIONS OF INSECTS. 



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 ge- 

 nus have the same habit. 



The aerial progress of the fly tribes (Aluscidce), in- 

 cluding the gad-^'\es (CEstrus) ; horse-flies (Tabanus); 

 carrion-flies (Musca), and many other genera — which 

 constitute the heavy horse amongst our two- winged fliers 

 — is wonderfully rapid, and usually in a direct line. An 

 anonymous observer in Nicholson' s Journal^ calculates 

 that, in its ordinary flight, the common house-fly (Musca 

 dmnestica^ L.) makes with its wings about 600 strokes, 

 which carry it five feet, every second. But if alarmed, 

 he states their velocity can be increased six or seven- 

 fold, or to thirty or thirty-five feet, in the same period. 

 In this space of time a race-horse could clear only ninety 

 feet, which is at the rate of more than a mile in a minute. 

 Our little fly, in her swiftest flight, will in the same space 

 of time go more than the third of a mile. Now com- 

 pare the infinite difl'erence of the size of the two animals 

 (ten millions of the fly would hardly counterpoise one 

 racer), and how wonderful will the velocity of this mi- 

 nute creature appear ! Did the fly equal the race-horse 

 in size, and retain its present powers in the ratio of its 

 magnitude, it would traverse the globe with the rapi- 

 dity of lightning. 



It seems to me, that it is not by muscular strength 

 alone that many insects are enabled to keep so long 

 upon the wing. Every one who attends to them must 

 have noticed that the velocity and duration of their 



" 4to. iii. 36. 



