AN AUGUST SONG 211 



arranged after the chirp, causing the second sound 

 to be slightly raised ; and in these instances the 

 following chirp is of the ordinary kind. Thus a 

 kind of alternation of these two chirps may be 

 maintained by one insect. It would be interesting 

 to know whether any of these crickets prolongs 

 the repetition to the extent of four or five sounds 

 given in one cry. This would indicate an advance 

 from the simple to the complex, in the same way 

 that birds seem to have progressed in song. 



The grasshopper, also, has a suggestive variation 

 of " time " in song. One may count the number 

 of sounds in the song of this insect, as one may 

 number those in the rapid song of a bird, by 

 reckoning every fourth sound ; in this way the 

 varying length of the insect's songs may be 

 ascertained. But there are other variations. On 

 hot days the insect sometimes produces slow, 

 single sounds by moving the legs alternately ; 

 anon both legs may be vibrated rapidly at the 

 same time, or they may be used together slowly. 

 These slow movements are the more interesting 

 because they seem to be so deliberate. We shall 

 never know whether the original grasshoppers 



