382 INSECT HEARING. 



seing that nature is not lavish of superfluities. In respect to 

 insects it is probable that a large number (especially of those leading 

 a parasitic life) seldom have occasion to use them if they have them. 

 In the case of other insects, on the contrary, a good musical ear 

 must be of essential advantage. For the males of the grasshopper, 

 cricket, and locust tribes are able to produce loud sounds, and it 

 seems placed beyond doubt that such personal and voluntary 

 exercise of sound producing power, is directly instigated by the 

 desire to make themselves agreeable to the females : consequently 

 these latter must exercise a faculty of hearing if they respond to 

 the cry of the male, and must, moreover, be able to distinguish 

 this cry from all other sounds occurring at the same time. 



6. In comparing the insect tympanal structure with the 

 mammalian ear, all resemblance is limited to the tympanal membrane, 

 and in more distant degree the tracheal expansion behind the 

 tympanal membrane may perhaps compare with the mammalian 

 tympanal cavity (middle ear). But nothing resembling the nerve 

 ^''scala" distributed over the tracheal sac is to be seen in the ear of 

 the mammal. 



The fact that the removal of these earlike organs does not destroy 

 the insect's sensitiveness to sound, and that mute species possess 

 the very same apparatus as the cUrping species, makes the whole 

 question still more puzzling. Our final conclusion is that the 

 tympanal apparatus of Acridia, which earlier naturalists looked upon 

 as an organ for increase of resonance, stands in close relation with 

 the well known drum of the cicada, while the tympanum of the 

 grasshoppers and crickets are homologically connected organs 

 which occur also in certain Lepidopteray which latter possess, in 

 addition, a peculiar and little known sensory organ at the bottom 

 of the abdomen, which is formed by a bundle of cuticular hairs. 



