26 The Book of Bugs, 



hold your job, the case is different. Even though the 

 fly's foot may be no more marvelous than a postage stamp, 

 its wings and eyes are not without merit. 



Other insects have two pairs of wings, but the fly has 

 only one pair, with a scallop on the rear edge of each, 

 which shows that the rear pair went into the discard. 

 These scallops are called haltcrcs or balancers, and it is 

 the theory of some that they help the fly to steer. They 

 say that when the starboard balancer is clipped off it 

 puts the fly hard a-starboard and similarly with the port 

 balancer. Under each of these scales is a globe on a 

 slender stalk fringed with fine hairs, believed to be sensi- 

 tive to odors. These globular processes pump air into 

 the veins of the wings to keep them taut and stiff, for 

 thin though the fly's wing may seem, it is nevertheless a 

 double texture. Perhaps clipping off the balancer lets 

 the wind out of the wing and so disables it. A fly is able 

 to saunter along through the air at the rate of five feet a 

 second, but when it is in a particular hurry it can go about 

 thirty-five feet a second, which is a 2.30 gait. Its wings 

 beat the air about 675 times a second. How do you 

 suppose they found that out? How would you go about 

 it to count 675 times a second? Couldn't say the num- 

 bers that fast, could you? Give it up? I am astonished 

 at you. 1 am really. Nothing simpler. Listen to the 

 musical note made by the fly's wings. Find the same 

 note on the piano. It is about E, first line of the treble 

 clef, which is made by 675 vibrations a second. When 

 the fly gets excited and cannot break away from the fly- 

 paper, it makes its thorax vibrate at a livelier rate. You 

 have heard people talk about Campanini's being able to 

 sing high C with chest voice. He could not, nor any 

 other man but a fly can. 



We do not know much of the house-fly's general intel- 



