THE CANADIAN ENTOMOLOGIST. 



215 



in. — Rate of Chirping. 



In producing the sound the wings are raised nearly at a right angle 

 with the body, and then scraped firmly across each other. The sound is 

 either a single chirp, or much more commonly a succession of chirps, 

 which follow one another at regular intervals, and vary in number, in the 

 cases observed by me, from 5 or 6 to 2,640. Six hundred to a thousand 

 is the more usual number. The term "chirp," as u?ed in the following 

 pages, refers to a single element of such a series. If the rate of chirping 

 is 120 per minute, the chirps occur at intervals of half a second. I have 

 estimated that one-third' of this time, or one-sixth of a second, is occupied 

 in producing the sound, while the remainder is the period of silence 

 between chirps. If the rate is only 60 per minute, the time occupied by 

 the sound is one-third of a second. The rate of sound vibration in this 

 case is much slower, and the pitch is correspondingly lower. 

 a. — Effect of Temperature on Rate. 



From the hundreds of observations made, a representative group is 

 shown in Table I. The temperatures are those at an elevation of six feet, 

 the average elevation of the insects. The temperature at two feet 

 elevation was generally about half a degree lower, that at ten feet half a 

 degree higher than that at six feet elevation. The temperatures computed 

 from Dolbear's and Bessey's formulas are added for comparison. 



Table I. — Showing rates of chirping of various individuals of 

 CEcaiithiis niveus at different temperatures and elevations : 



