216 TJTE CANADIAN ENTOMOLOCxIST. 



It is seen that there is a general correspondence between rate and tem- 

 perature. But that the rate does not follow any law based on temperature 

 is apparent from the observations for Aug. 27 and Sept. 7 (first record), 

 where the rates are the same with a difference of temperature of over nine 

 degrees. Furthermore, comparison of Aug. 27 and Aug. 28 shows that 

 of two records the higher rate may accompany the lower temperature. 

 The five records for Sept. 7 were made within an area of two square rods 

 in the same blackberry patch. The crickets were chirping simultaneously, 

 and the observations were made within a pep'od of 15 minutes; the 

 temperature did not change perceptibly, yet the rate in different individuals 

 is from 93 to no. Other records made outside of this area on the same 

 evening showed even greater extremes, the lowest rate being 84 per 

 minute, the highest 126. These observations are of interest in the light 

 of Dolbear's observation of accurate synchronism. 



It will be noted that the crickets of Sept. 7 were at different eleva- 

 tions, and that those at the greater height chirped the more rapidly. 

 While there were numerous exceptions to tliis correlation of rate with 

 elevation, the higher crickets chirped at rates which on the average were 

 markedly higher than the average of individuals nearer the ground. 

 Dolbear might have explain^^d this difference of rate at different elevations 

 by the fact that the greater elevations have the higher temperatures. Even 

 if temperature is the cause of the variations at different altitudes, the 

 synchronism existing among ''all the crickets in a field" would be 

 destroyed, for to produce such synchronism it would be necessary to have, 

 not merely a level field, but all the crickets in the same horizontal plane 

 over the field. Granting for the moment that temperature alone is 

 responsible for these differences in rate, Dolbear's formula, which is not 

 much in error in making the rate increase by 4 per degree rise in 

 temperature, does not state the proper relation between the difference of 

 temperature and the difference of rate. The observed difference of 

 temperature between elevations of 2 ft. and 10 ft. was usually about i" at 

 the time of making these observations, 7.30 to 8 p.m. Hence, according 

 to Dolbear's formula, or any formula based on crickets at the same 

 elevation, the difference in rate between elevations of 2 ft. and 10 ft. should 

 have been about 4, whereas it v/ill be seen from the table that the 

 difference was 17. 



Evidently individual rates are not closely correlated with temperature. 

 If any accurate correlation exists, it ought to be ap[)arent from average 

 rates. A few averages, covering, with some additions, the same period 



