292 TEXT-BOOK OF ENTOMOLOGY 



rods. In the opposite direction a fine, ligament (cZ) passes from eg to the skin ; 

 in this way the auditory organ is suspended in a certain state of tension, and is 

 favorably situated to receive even very fine vibrations. A similar apparatus 

 has been detected in the larva of Ptychoptera. 



Antennal auditory hairs. It is not at all improbable that the 

 antennae of different insects contain auditory as well as olfactory 

 structures. Lubbock has suggested that the singular organs which 

 have only been found in the antennae of ants and certain bees, and 

 to which he gives the name of " Hicks' bottles " (Fig. 281), may act 

 as microscopic stethoscopes, while Leydig also regards them as 

 chordotonal organs. 



That, however, some of the antennal hairs of the mosquito, as first 

 suggested by Johnson and afterwards proved experimentally by 

 Mayer, are auditory, seems well established. Fastening a male 

 mosquito down on a glass slide, Mayer then sounded a series of 

 tuning-forks. With an Ut 4 fork of 512 vibrations per second, some 

 of the hairs were seen to vibrate vigorously, while others remained 

 comparatively at rest. The lower (Ut 3 ) and higher (Ut 5 ) harmonics 

 of Ut 4 also caused more vibration than any intermediate notes. 

 These hairs, then, are specially tuned so as to respond to vibra- 

 tions numbering 512 per second. Other hairs vibrated to other 

 notes, extending through the middle and next higher octave of the 

 piano. 



Mayer then made large wooden models of these hairs, the one 

 corresponding to the Ut 3 hair being about a metre in length, and on 

 coimting the number of vibrations they made when they were 

 clamped at one end and then drawn on one side, he found that it 

 "coincided with the ratio existing between the numbers of vibra- 

 tions of the forks to which covibrated the fibrils," or hairs. It 

 should be observed that the song of the female mosquito corresponds 

 nearly to this note, and would consequently set the hairs in vibra- 

 tion. Mayer observed that the song of the female vibrates the hairs 

 of one of the antennae more forcibly than those of the other. Those 

 auditory hairs are most affected which are at right angles to the 

 direction from which the sound comes. Hence from the position of 

 the antennae and the hairs a sound will be loudest or most intense if 

 it is directly in front of the head. If, then, the song of the female 

 affects one antenna more than another, the male turns his head until 

 the two antennae are equally affected, and is thus able to fly straight 

 towards the female. From his experiments Mayer found that the 

 male can thus guide himself to within 5 of the direction of the 

 female. Hence he concludes that "these insects must have the fac- 



