92 AN INTRODUCTION TO ENTOMOLOGY 



Landois believed that the spiracular organs referred to above were 

 the source of the acute sound. But more recently Perez ('78) and 

 Bellesme ('78) have shown that when the spiracles are closed artifi- 

 cially the insect can still produce the high tone. Perez attributes the 

 sound to the vibrations of the stumps of the wings against the solid 

 parts which surround them or of the sclerites of the base of the wing 

 against each other. But Bellesme maintains that the sound is pro- 

 duced by changes in the form of the thorax due to the action of the 

 wing-muscles.* When the wing-muscles are at rest the section of this 

 region, according to this writer, represent an ellipse elongated ver- 

 tically; the contraction of the muscles transforms it to an ellipse 

 elongated laterally; the thorax, therefore, constitutes a vibrating 

 body which moves the air like a tine of a tuning fork. Bellesme 

 states that by fastening a style to the dorsal wall of the thorax he 

 obtained a record of the rate of its vibrations, the number of which 

 corresponded exactly to that required to produce the acute sound 

 which the ear perceives. 



The fact that the note produced when the wings are removed is 

 higher than that produced by the wings is supposed by Bellesme to be 

 due to the absence of the resistance of air against the wings, which 

 admits of the maximum rate of contraction of the wing-muscles. 



g. MUSICAL NOTATION OF THE SONGS OF INSECTS 



Mr. S. H. Scudder ('93) devised a musical notation by which the 

 songs of stridulating insects can be recorded. As the notes are always 

 at one pitch the staflE in this notation consists of a single horizontal 

 line, the pitch being indicated by a separate statement. Each bar 

 represents a second of time, and is occupied by the equivalent of a 

 semibreve ; consequently a quarter note f, or a quarter rest 1, repre- 

 sents a quarter of a second ; a sixteenth note t. or a sixteenth rest i 

 a sixteenth of a second and so on. For convenience's sake he intro- 

 duced a new form of rest, shown in the second example given below, 

 which indicates silence through the remainder of a measure; this 

 differs from the whole rest commonly employed in musical notation 

 by being cut off obliquely at one end. 



*This view was maintained by Siebold at a much earlier date in his Anatomy 

 oj the Invertebrates. 



