THE SENSE ORGANS OF INSECTS. . 31 



attached to that of the male is evident, or why such very 

 speciaHsed development in this sex as against that of the 

 ordinary female ? There is no need for this development for the 

 purpose of scent, because, as shown by Mr. Arkle, scent can only 

 be demonstrated to the animal through its breathing-organs ; 

 and touch is as necessary to the female as to the male, for where 

 we find antennae used for touch we find these organs equally 

 developed in both sexes, as in Khopalocera, Hymenoptera, &c. 



That there is no impossibility in the possession of an 

 additional sense, we have proof in the pituitary body of verte- 

 brate embryos found at the anterior imrt of tJte nervous sijstem, 

 and which cannot now be accounted for other than as the last 

 vestige of an organ functional to a sense now unknown to verte- 

 brates, but possessed in full vigour by the vertebral prototype. 

 If there be another sense, it is possible it is located in the 

 antennae. That a structure originally developed for one special 

 function can become partly or wholly atrophied, and later take 

 on a function entirely different from its original one, we also have 

 abundant proof. One of the gill-clefts of fishes, found in the 

 highest developed fishes as merely slits and functionally used in 

 breathing water, is found in all vertebrates higher developed than 

 fishes, as the Eustachian tube and the meatus auditorius, quite 

 open in some rare cases, and, in cases of fracture of the tympa- 

 num, as a tube from the throat to the external ear ; the external 

 half of this cleft has been diverted from its original function to 

 that of a sound-channel, to carry the vibrations from the external 

 ear to the tympanum, which is a thin film dividing the tube, so 

 that sound-waves coming along it strike the tympanum and 

 cause it to vibrate. When, through shock or concussion, the 

 tympanum is fractured, air or fluid in the throat can be forced 

 along this Eustachian tube through the ear; this act is analo- 

 gous to the expulsion by fish of water in their mouth through 

 their gills. 



Mr. Arkle says that Lepidoptera do not hear ; that a gun 

 report does not startle them, it produces no symptoms of alarm. 

 Is it not possible that there are qualities of sound to which these 

 insects are sympathetic, and that such qualities have not yet 

 been produced by artificial means, and are beyond the power of 

 human ears to record ? This is merely a speculation as perhaps 

 bearing on the use of the antennae, as we know that the very 

 piercing squeak of the bat has so many vibrations to the second 

 in its harmonic composition that it is beyond the power of the 

 ordinary human ear to become sympathetic with it, and there- 

 fore the squeak is inappreciable usually to our ears. 



That it is not beyond the region of possibility that the 

 antennae of Heterocera play some part in the exercise of hearing 

 is borne out by the investigations of Mayer, Landois, and Hurst 

 in regard to Calex, the gnat. It is now admitted that the singing 



