THE CANADIAN ESNTOMOLOGIST. 223 



Tke table of the rate of chirping of the individual cricket shows that 

 the rates of even an individual are not closely correlated with temperature. 

 In fig. 15, the fact that one of the solid lines lies, throughout the greater 

 part of its length, above the other shows that the rate of one cricket is 

 almost constantly higher than that of the other. This can hardly be 

 explained except by individuality. The crossing and recrossing of the 

 two lines must then be explained by another factor (physiological state) 

 which I discuss in another place. 



IV. — Synchronism. 

 I found exact synchronism to be comparatively rare, and to exist 

 only between neighbouring crickets. When accurate synchronism did 

 occur, it affected usually only two individuals, sometimes three. One 

 evening I discovered two crickets about five feet apart chirping in such 

 accurate unison that I did not at once realize that there were two crickets. 

 One soon stopped ; the second hesitated, its chirp became weak, and it 

 even lost a beat. After an irregular solo of several minutes, the second 

 cricket recommenced. At the first chirp the first cricket struck a note 

 out of time, then lost a beat, as if startled. It next voiced a half-dozen 

 weak, uncertain chirps, then the call gradually grew in intensity, until the 

 two crickets were again chirping in exact unison. 



V. — Summary. 



1. While there is a general correspondence between temperature and 

 rate of stridulation, there are numerous variations of rate that cannot be 

 accounted for by differences of temperature. Dolbear's formula cannot be 

 applied to my observations without a possible error of 6^.65. 



2. Rate of stridulation is in no way correlated with wing-length. 



3. Humidity seems to affect rate of chirping, but the evidence is not 

 conclusive. 



4. The rate of chirping of different crickets under the same external 

 conditions depends on their individuality. 



5. Synchronism is rare, and is observable in only two or three 

 individuals near one another. 



VI. — Discussion, 

 It is clear that Dolbear's and Bessey's laws are only approximately 

 accurate. Temperatures computed from them may be expected to vary 

 from observed temperatures as much as 6^.65 with the first formula, and 

 g°.69 with the second. Any expression for the rate of chirping must be a 

 function of several independent variables, of which temperature is only 



