THE FACULTY OF HEARING. 3^7 



and they considered the apparatus to be a true auditory organ. 

 But it does not appear whether they regarded it as solely and 

 especially adapted for reception of the peculiar insect cry, — that is 

 as a musical ear simply — or as possessing the general character of 

 an apparatus adapted for transmission and perception of every kind 

 of vibration which might in any way affect the sensory conscious- 

 ness of the insect. 



Franz Leydig in his excellent treatise on the organs of taste and 

 hearing in insects and crabs, remarks that great caution should be 

 exercised in pronouncing upon the character of these tympanal 

 organs, notwithstanding their " prima facie " claim to be considered 

 auditory in function. Thoagh they have been found only in 

 Locusta, GrilUdcB, and Acridia, he considered it probable that 

 similar organs would be discovered in other insects. He does not 

 attach much importance to the circumstance that they are not 

 placed in the head or antennae, which seems to constitute an 

 objection in the minds of all who believe that the antennae should 

 be the proper locality of an auditory organ. 



Until 1875 ^^^ tympanal structure was accepted by all authorities 

 on the subject as the true and sole insect ear. Prof. Brunner, 

 however, in his essay on the external organ of hearing of Orthoptera, 

 limits the auditory function to the recognition of the cry of the 

 male by the female. But the female Acridia possess the organ, 

 though the males utter no sound. On the other hand it appears 

 to be wanting in all mute species of grasshoppers and locusts, and 

 rudimentary in several voiceless species. Considered therefore 

 from the point of view of inconstant occurrence a difficulty presents 

 itself, namely, that if this tympanal organ be the true and sole ear 

 of these three groups of Orthoptera, it should follow that every 

 species in which it was wanting or rudimentary must be deaf ; 

 incapable, that is, of hearing either the musical notes of its related 

 species, or any other noise or tones of any kind which surround it. 

 The only alternative that offers is that other auditory organs may 

 co-exist with the tympanal structure. 



