90 INSECT MISCELLANIES. 



which were at a good distance from the spot where 

 we stood, — the primary cause, perhaps, of their flying 

 high*. 



"That purely rural, little noticed, and, indeed, 

 local occurrence," says Mr. Knapp, "called by the 

 country people ' hummings in the air,' is annually 

 heard in one or two fields near my dwelling. About 

 the middle of the day, perhaps from twelve o'clock 

 till two, on a few calm, sultry days in July, we occa- 

 sionally hear, when in particular places, the humming 

 of apparently a large swarm of bees. It is generally 

 in some spacious open spot that this murmuring first 

 arrests our attention. As we move onward the sound 

 becomes fainter, and by degrees is no longer audible. 

 That this sound proceeds from a collection of bees, or 

 some such insects, high in the air, there can be no 

 doubt ; yet the musicians are invisible. At these 

 times, a solitary insect or so may be observed here and 

 there, occupied in its usual employ, but this straggler 

 takes no part in our aerial orchestra*." 



The buz of flies has been found no less difficult to 

 explain than the hum of bees. That it is not pro- 

 duced by the wings alone striking upon the air, is 

 proved from the fact of many insects of rapid flight, 

 such as the dragon flies {LibeUulina) and the crane 

 flies (Tipulidce) , flying silently. Some flies, again, 

 are able to produce a loud buz when not on the 

 wing. Of this, an instance has recently occurred 

 to us in the wasp fly {Chrysotoxiim fasciolatum, 

 Meigen), which had got into our study, and kept up 

 its peculiar buz when resting, apparently motionless, 

 on the window-frame ; yet, when we observed it mi- 

 nutely, there was still a perceptible vibratory tremor 

 in the wings, similar to that of a harp-string, but so 

 rapid as at first to escape the eye. The same buz 



* J.R. 

 t Journ. of a Naturalist, p. 376, 3d edit. 



