114 THE ENTOMOLOGIST. 



these sounds. The longest fibres vibrated sympathetically to 

 the grave notes, and the short fibres vibrated sympathetically 

 to the higher notes. The fact that the nocturnal insects have 

 highly organized antennae, while the diurnal ones have not, 

 and also the fact that the anatomy of these parts of insects 

 shows a highly developed nervous organization, lead to the 

 highly probable inference that Prof. Mayer has here given 

 facts which form the first sure basis of reasoning in reference 

 to the nature of the auditory apparatus of insects. These 

 experiments were also extended in a direction which added 

 new facts to the physiology of the senses. If a sonorous 

 impulse strike a fibre so that the direction of the impulse is 

 in the direction of the fibre, then the fibre remains stationary. 

 But if the direction of the sound is at right angles to the fibre, 

 the fibre vibrates with its maximum intensity. Thus, when a 

 sound strikes the fibrils of an insect, those on one antenna 

 are vibrated more powerfully than the fibrils on the other, and 

 the insect naturally turns in the direction of that antenna 

 which is most strongly shaken. The fibrils on the other 

 antenna are now shaken with more and more intensity, until, 

 having turned his body so that both antennae vibrate with 

 equal intensity, he has placed the axis of his body in the 

 direction of the sound. Experiments under the microscope 

 show that the mosquito can thus detect to within five degrees 

 the position of the sonorous centre. To render assurance 

 doubly sure, Prof Mayer, having found two fibrils of the 

 antennae of a mosquito which vibrated powerfully to two 

 different notes, measured these fibrils very accurately under 

 the microscope. He then constructed some fibrils out of 

 pine wood, which, though two or three feet long and of the 

 thickness of small picture-cord, had exactly the same pro- 

 portion of length to thickness as the fibrils of the antennae of 

 the mosquito. He found that these slender pine rods or 

 fibrils had to each other the same ratio of vibration as the 

 fibrils of the mosquito. — '■American Naturalist^ vol. viii. 

 p. 236. 



British Aphides requested. — For the last two years I have 

 been engaged in describing and drawing from life all the 

 British Aphides that have come under my notice. May I 

 ask, through your pages, such co-operation from our entomo- 

 logists as they may have it in their power to give ? 1 shall 



