380 INSECT HEARING. 



3. That crickets respond to very different kinds of sounds 

 (noises or tones), provided that they are loud and sufficiently near, 

 and when not too many vibrations of different character are 

 impressed upon them at the same time. 



4. That they hear better by night than by day. The perception 

 of sound is generally proportional to the intensity of its impression 

 and the previous absence or weakness of sounds, 



5. Certain noises and tones, e.g., screeching and scratching 

 and generally very intense sounds excite painful emotions, and the 

 insects are morbidly irritated, throw themselves wildly about and 

 shake their limbs convulsively. 



6. Sensitiveness to sound is not destroyed by extirpation of the 

 tympanal organs, so far as can be judged from the fact that reflex 

 actions still continue. 



7. The perception of sound without a tympanal organ extends 

 to the following kinds, i — All rustling noises ; 1 — high notes of 

 the violin lightly drawn, and resembling in pitch the sounds which 

 they themselves hear -, 3 — their own sounds, for that mutilated 

 insects hear the sounds made by their neighbours is obvious from 

 their showing signs of restlessness, by moving their antennae or 

 even by tremblings of the whole body. 



8. Crickets deprived of their tympanal organs distinguish not 

 only the loudness of sound but the pitch also, for when violin notes 

 are played in scale some notes produce stronger reflex actions than 

 others. And from this it may be inferred that the particular parts 

 of their integument which subserve, in the first instance, the 

 reception of vibrations, are brought into consonating vibration only 

 by certain notes, and therefore transmit these to the proper nerve 

 elements rather than other notes to which they are not attuned. 



Dr. Graber further considers it probable that the seat of sound- 

 perception is in the head. 



In a small popular account of the insect organism by Professor 

 V. Graber, published in 1871, certain conclusions are given 

 respecting insect hearing and organs of hearing, of which the 

 following is a full abstract : — 



