THE CA.NADIA.N ENTOMOLOGIST. 



2lV 



as in Table I, have been calculated, and are given, together with the 

 temperatures computed from Dolbear's and Bessey's formulas, in Table II. 

 Table II. — Showing averages of the rates of ten to fifteen individuals 

 of CEcanthus iiiveus at different temperatures : 



Here it appears again that, even when averages are taken, approxi- 

 mately equal rates may accompany widely-differing temperatures (cf. Sept. 

 I and Sept. 8), and tliat the higher rate may occur with the lower' tem- 

 perature (cf. Aug. 27 and 28), though in both cases the discrepancy is less 

 marked than in Table I. 



It seems tiiat while tiiere is a general agreement between temperature 

 and rate of chirping, yet it is not possible to express this agreement by 

 any formula. Any temperature calculated from the rate by Dolbear's 

 formula may be over six degrees in error, and over nine degrees when 

 Bessey's formula is used. It follows also from these observat'ons that 

 there can be no accurate synchronism. 



b. — Effect of Wing Length on Rate. 

 In attempting to explain the discrepancies noted above, wing length 

 suggested itself as a possible factor. The effect of wing length was 

 determined as follows : The rates of a number of individuals, say ten or 

 fifteen, were determined, usually within a period of 40 minutes, and the 

 average was computed. One member of the series, whose rate was of 

 course known, was captured, and its wings were measured. Measurement 

 was made by laying the wing, after removal from the body, on a scale 



