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 antenne, 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 antenne 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 
antennz 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 antenne 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. 
. 236. 
r 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 
