Hudson. — On the Senses of Insects. 23 



strong reason to believe that, even in the same animal, this 

 sensitiveness to sounds is not necessarily confined to one 

 part. 



From the above it will be seen that there are good reasons 

 for supposing that the organs of hearing are situated in the 

 antennae of insects, and there is much to support this view, 

 though modern investigation has revealed the existence of 

 well-developed organs of hearing on other parts of the body. 

 Before relating a few of the experiments which have been 

 made in connection with the power of hearing in insects it 

 will, perhaps, be well to very briefly describe the curious ears 

 which have been discovered on the tibiae of the anterior legs 

 in many grasshoppers, and which are very well developed 

 and easily seen in the specimens of one of our native wetas, 

 which I have pleasure in exhibiting this evening. The re- 

 searches of Muller, Siebold, Leydig, Hensen, Graber, and 

 Schmidt conclusively prove that these drum-like organs are 

 veritable ears. In grasshoppers and crickets the auditory 

 organ lies in the tibia of the anterior leg, on both sides of 

 which there is a disc generally more or less oval in form, and 

 differing from the rest of the surface in consisting of a thin, 

 tense, shining membrane, surrounded wholly or partially by 

 a sort of hame or ridge. 



If now we examine the interior of the leg, the trachea, 

 or air-tube, will be found to be remarkably modified. Upon 

 entering the tibia it immediately enlarges and divides into 

 two branches, which reunite lower down. To supply air to 

 this wide trachea the corresponding spiracle, or breathing- 

 hole, is considerably enlarged, while in the dumb species it is 

 only of the usual size. The enlarged trachea occupies a con- 

 siderable part of the tibia, and its wall is closely applied to 

 the tympanum, which thus has air on both sides of it, the 

 open air on the outer the air of the trachea on its inner 

 surface. In fact, the trachea acts like the Eustachian tube 

 in our own ear : it maintains an equilibrium of pressure on 

 each side of the tympanum, and enables it freely to transmit 

 the atmospheric vibrations. 



On the 17th January, 1890, I made the following experi- 

 ment on a female specimen of weta (Deinacrida megacephala), 

 an insect possessing well-developed ears on the tibiae of its 

 anterior legs. 11.20 a.m. : I placed the insect on a board 

 suspended from the ceiling, where no vibrations except those 

 of sound could reach it. First I tried a piano, but insect 

 did not appear to hear either treble or bass notes. Then 

 tried beating a kerosene-tin with an iron rod, but apparently 

 insect could not hear noise except when the sounds were 

 very rapidly made and of loud pitch. At this stage the 

 insect seemed to wake up and put out its antennae and palpi. 



