ON INSECT SOUNDS. 239 



Sometimes additional sounds are heard with the wing-tone, as, 

 e.g. in the red-winged grasshopper Pachytylus Stridulus, where the 

 clicking sound produced by friction of the root of the posterior 

 wing against the wing-cover predominates. The contrary may be 

 observed in Stratiomya Chameleon (water fly) where the wing tone 

 overpowers an accompanying crackling or rustling sound of the 

 roots of the wing. 



A different method of producing sound, by vibration of the 

 insect's wing, is that which closely resembles the , bowing of a 

 stringed instrument, as noticed in the friction tone of the cricket 

 where the anterior pair of wings, or elytra, are set in vibration by 

 the friction of their file notched ribs. Any difference of tone in 

 these insects can only be caused by slower or more rapid friction — 

 every individual keeps generally to one note, but those which are 

 smaller make a finer note than the larger individuals. The same 

 occurs in the grasshopper whose wing cases are set in vibration 

 by friction of the thighs of the third pair of legs. — Forte and 

 piano, crescendo, decrescendo, as well as a rise of tone by more 

 rapid friction, are possible with this arrangement. 



3. The number of vibrations of the insect's wing is far too rapid 

 to be counted by sight, except in a very few cases. But this 

 difficulty may be solved in two ways. — 



Marey in his Memoir on the Flight of Insects and Birds, (ann : 

 des Sciences Natur: /Jth Ser. Zool, T. xii., p. 49,50), was the first 

 to determine the number of vibrations by help of a graphic method. 

 The insect was so fixed as to allow the tip of its wing to remain in 

 contact with the smoked surface of a cylinder, which was set in 

 motion by clockwork. Each movement of the wing swept the 

 smoked surface of the advancing cylinder, leaving its line of contact 

 visibly marked. In this way M:irey found that the greatest 

 number of vibrations was that of the house fly, viz., 330 in a second, 

 and the least number that of the cabbage butterfly, viz., 9, Marey 

 considers that the number of vibrations cannot be ascertained by 

 determining the note, because the hum of the insect arises from 



