224 THE CANADIAN ENTOMOLOGIST. 



one. Hence, its graphical representation is not a line, nor even a surface. 

 Of the other possible factors in addition to temperature, it has been shown 

 that wing-length is of no eftect in determining the rate of chirping. The 

 remaining two factors wliich have been studied, namely, humidity and 

 individuality, are, with temperature, sufficient to explain most of the 

 observed facts flowever, in fig. 15 there remains still one point to be 

 explained. That point is the crossing of the curves of the individual 

 crickets. The external factors of temperature and humidity have been 

 eliminated by having them practically the same for both crickets. 

 Individuality has not served to teep the curves separate throughout their 

 length. Here some other factor, either external or internal, must enter. 

 The most plausible explanation seems to be that based on differences of 

 j)hysiological state, which, of course, could not be determined from my 

 observations. It is quite possible that physiological condition (age, 

 hunger, sexual condition, etc.), plays an important role. It may well so 

 have affected "rate individuality" as to have caused the crossing of the two 

 .curves plotted in fig. 15. 



The synchronism found by Dolbear does not appear in my observa- 

 tions. As a rule, even neighbouring crickets chirp at rates that are very 

 noticeably different. The instance of synchronism recounted above 

 throws some light on the question, which by implication Edes (1899) 

 raises, as to wliether synchronism is due to the effect upon various 

 individuals of equal temperatures or other conditions. It seems from my 

 observation that synchronism may possibly be due rather to the effect of 

 each cricket's chirp upon the other cricket. 



Dolbear may have gained his impression of universal synchronism 

 by observing a si^oradic case of it or by actually listening to but one 

 cricket and mistaking it for a full chorus. The intensity of sound 

 diminishes so rapidly with increasing distance from the source, that witii 

 but one cricket chirping several feet away and the others at a greater 

 distance an observer could easily overlook those at the greater distance. 

 One cricket, if undisturbed, will usually perform six to eight hundred chirps 

 without missing one, except on cool nights. Not infrequently it will 

 perform 1,500 in succession ; while one "long-winded" individual which I 

 observed continued through 2,640, another 2,425, a third 2,228. From 

 these figures it will be seen that breaks in the series of chirps might escape 

 observation, and that the continuous chirping of one performer might be 

 mistaken for a chorus in which the single crickets were not missed when 

 they dropped out. It would thus happen that a single cricket may have 

 been mistaken for several in unison, each performing less continuously. 



