INSECT HEARING. 379 



opening and shutting a penknife, striking on a key, &c. The 

 insect remained immoveable. At length I grasped a handful of 

 dry grass, making a rustling noise. Instantly the insect was in its 

 hole. Immediately over the hole by which another insect stood, I 

 made the same noises, rustled in the grass, fluttered the leaves of 

 my note book, whistled, &c. The insect remained motionless but 

 instantly took to flight as I struck the ground with my fist. 



In the gloaming I crept quietly into a clump of alder bushes 

 where from every twig came the chirp of the locus fa cantans. The 

 insects appeared to perceive the least rustle of leaf or grass, but 

 standing still a little until the chirping began again. There were 

 two sounds the loud chirping tone and then a kind of light echo . 

 When the chirp is in fall swing it goes on in songs of six to seven 

 minutes' duration broken by pauses of two to three minutes. I 

 caught several of these insects putting each in a separate glass. 

 From one of them was cut off the front pair of legs. The 

 uninjured insects began to chirp again the next day ; the mutilated 

 one was not heard before the next day. 



As respects different kinds of noise, I could not find any 

 difference between the hearing of uninjured and injured insects. 

 They seem very sensitive — ceasing their chirp regularly when I 

 attempted to imitate their own noises by rapid friction of a knife 

 blade on a ground glass plate, or scratched on a wall. When such 

 sounds are produced, the insects stop their chirping for a longer 

 time. The injured insects chirped comparatively seldom when 

 isolated, but often when in company with other insects it almost 

 seemed as if it answered its neighbours. 



The facts which Dr. V. Graber believes that he has established 

 by the experiments above described are thus summed up — 



I. That the sensitiveness to vibrations of sound, as well as to 

 mechanical excitement of the organs of feeling, is very unequal in 

 different individuals. 



3. That this sensibility increases when the nervous system is 

 irritated by any kind of injury. 



