236 SENSES OF INSECTS. 
Bonnet, however, thought them deprived of hearing? ; 
but numerous observations prove the contrary. That 
they hear in their darva state, is evident from facts stated 
by the latter physiologist. He found that the sound of 
his voice evidently affected some caterpillars; which he 
attributes, but surely without reason, to the delicacy of 
their sense of touch: at another time, when some cater- 
pillars of a different species were moving swiftly, he rang a 
small bell; upon which they instantly stopped and moved 
the anterior part of their body very briskly®. That 
they possess this faculty in their zmago state is confirmed 
still more strongly by facts. I once was observing the 
motions of an Apion under a pocket microscope: on see- 
ing me it receded. Upon my making a slight but di- 
stinct noise, its antenne started: I repeated the noise 
several times, and invariably with the same effect. A 
Harpalus, which I was holding in my hand, answered 
the sound in the same manner repeatedly. Flies, I have 
observed, at brisk and distinct sounds move all their 
legs; and spiders will quit their prey and retire to their 
hiding places. Insects that live in society give notice 
of intended movements, or assemble their citizens for 
emigration by a certain kum*. But the most satisfactory 
proof of the hearing of these animals is to be had from 
those Orthoptera and Hemiptera whose males are vocal. 
Brunelli kept and fed several males of Acrida viridissima 
(a grasshopper with us not uncommon) in a closet, which 
were very merry, and continued singing all the day; but 
a rap at the door would stop them instantly. By prac- 
tice he learned to imitate their chirping: when he did 
* Syst. Nat. 1.535. Bonnet Guvr. ii. 36. b Thid, 
Vor pal63: 
