Generation of Sounds by Canadian Insects. 129 



dread by the Vulgar in several parts of Europe, its appearance be- 

 ing regarded an ill omen, or harbinger of approaching fate. 

 With the Death's-head moth, this sound is given out when confined 

 or taken into the hand, and is likened to the cry of a mouse, but 

 is said to be more plaintive and even lamentive. 



The humming noise of many, if not of most of the Canadian 

 sphinges, some good specimens of which were in my collection, is 

 distinctly heard during their rapid flight, but it is again different 

 from the stridulous and plaintive note emitted by them when sta- 

 tionary. The mode in which this sound is produced has not as 

 yet been correctly ascertained. It has been supposed by Reaumur 

 to be caused by rubbing the palpi against each other, and by 

 Lorey to be owing to the rapid escape of the air from the two 

 ventral cavities. On carefully considering the matter, there cannot 

 be any doubt that the sound is connected with the respiratory 

 organs, but in what manner it is produced, will probably never be 

 ascertained. I have no doubt if attention is paid to this point, 

 that one or more of the Canadian species may be found 'to emit 

 the sound before quitting their pupa-case, as Mr. Ha udon found 

 with the Death's-head moth. 



Although it is not always easy to detect the inode of produetio:> 

 of the sounds generated by different trite,, we have no difficulty 

 in rightly attributing the buzzing and humming noises beard 

 during the flight of the dipterous and hymenopterous insects, to 

 the forcible expulsion of the air -as it streams through the respira- 

 tory spiracles. The experiments of Burmeister on bees and flies 

 show that the noises are not so much produced by the simple 

 motion of the wings, to which it is commonly attributed, as by 

 the vibrations of a little membranous plate, situated in each of the 

 posterior spiracles of the thorax ; for if the apertures of these be 

 stopped, no sound is heard, even though the wings remain in 

 movement. These are the true vocal organs, although the full- 

 toned buzz is increased by the action of the wings ; yet many of 

 the species, as the wasp-fly for instance will buzz when at rest. 



The buzzing of the gad-fly Tabanus is familiar to horses and 

 cows'-, which are sometimes covered with blood from its attacks. 

 The shrill trumpet of the musquito gives us warning of the prox- 

 imity of that insect, which pursues us in many parts of Canada, 

 thirsting for our blood. The buzzing of numerous flies, including 



* The horse gad-fly Gastrus equi, whilst that affecting sheep is called 

 Oestrus ovis, or the sheep gad-fly. 



Canadian Nat. 4 Vol. IV. No. 2. 



