32 



THE ENTOMOLOGIST. 



of the guat over one's head in the damp ]anes is merely the 

 call of the female for the male ; this has heen investigated in 

 the living subject by Mayer and Landois, and histologically 

 demonstrated by Dr. C. Herbert Hurst, of Owens College, Man- 

 chester.* 



There is at the base of the antenna of the male gnat a cup- 

 shaped process, the highly pectinated antenna emerging from 

 the centre of the base of it. This cup is the external ear, and is 

 intimately connected with the nervous system. When a note is 

 given out, harmonically designated UT^ (512 vibrations to the 

 second), either naturally or artificially produced by a tuning-fork, 

 and the axis of the antenna is pointing in the direction from 

 which this sound comes, then the fine pectinations (setse) of the 

 antennae vibrate in unison to the sound-waves. This causes the 

 shaft of the antenna to contract and elongate with the vibration, 

 and thus a stimulus is set up and transmitted by the nerve of 

 the antenna to the very large cerebral ganglia. 



Landois has demonstrated that the female gnat has attached 

 to the spiracles two filaments (analogous to the vocal cords of 

 vertebrates), and, as in vertebrates also, when air is forced 

 through them, a sound is produced which has also 512 vibrations 

 or thereabouts to the second. Now let us apply the two things 

 together : suppose a gnat (female) is in a room, singing her song 

 of UT4 ; if there is in the room and within radius of the pene- 

 tration of this note a male, and its antennae are pointing in the 

 direction of the female, — and we have plenty of evidence that 

 they will soon do this, as its antennae are hardly ever still, but 

 always/ee/in(/ for its mate's song, — then the setae are set vibrating, 

 which is communicated down the shaft to the ear and from the 

 ear to the nervous system ; thus the male is apprised of the 

 nearness and direction of its mate. This susceptibility to sound 

 of the male antenna has been beautifully Avorked out by Mayer ; 

 Dr. Hurst (/. c.) says, "Mayer has performed some experiments 

 which throw a good deal of light on both these questions. 

 Having fixed a male gnat upon a slide, he examined the hairs on 

 the shaft of the antenna, and found that when certain notes 

 were sounded with tuning-forks certain hairs vibrated so that 

 their outlines became indistinct, and this effect was most marked 

 when the tuning-fork UT4 was sounded, giving 512 vibrations 

 per second, this note setting the greatest number of the large 

 hairs in violent vibration, but only when the sound came in such 

 direction as to strike the hairs at right angles, or nearly so — 

 that is to say, these hairs vibrate when this sound is produced at 

 a point towards which the antenna is pointing." 



Mr. Arkle says, "But assembling is evidently habitual in 

 species without these very antennae " ; and I would add to this 



* ' Transactions of the Manchester Microscopical Society,' 1890, " On the 

 Life-history and Development of a Gnat,' by G Herbert Hurst, Ph.D. 



