463 



air in the bottles must have averaged very considerably less as the 

 glass remained uniformly cold, and the probable temperature must 

 have been 60 degrees or less. The conditions under which the imag- 

 ines were confined were, of course, not natural, but indicate that the 

 length of life under more advantageous conditions may be even longer 

 than in this laboratory test and make it reasonably certain that it ex- 

 ceeds one to two days, as has been stated by various writers. A male 

 that emerged and failed to leave the water was allowed to lie on the 

 surface for twenty-four hours, at the end of which time it was still 

 alive. 



The duration of life of the eleven imagines that were confined in 

 the bottles is appended. 



Emerged Jan. 14, 1 female, 1 male; female died Jan. 21, evening, male, Jan. 22, 

 evening. 



Emerged Jan. 15, 1 female; died Jan. 25, evening. 



Emerged Jan. 16, 2 females; died Jan. 25, evening. 



Emerged Jan. 17, 2 males; one died Jan. 26, morning, the other Jan. 27, noon. 



Emerged Jan. 18, 1 male, 1 female; both died Jan. 28, male, morning, female, 

 evening. 



Emerged Jan. 19, 1 male, 1 female; both died Jan. 27, morning. 



The above record indicates an average duration of life of nine and 

 a half days. 



A female which emerged February 3 was left on the glass side of 

 the aquarium for the purpose of ascertaining whether the difference 

 between the air in this situation and that contained in the bottles used 

 in the other experiment would make any difference in the length of life 

 of the adult. The space between the water in the aquarium and the single 

 sheet of writing paper with which the latter was covered was about 

 two inches. This paper cover was laid loose on top, being held in posi- 

 tion by a small note-pad which did not cover the entire area of the 

 aquarium. Despite the fact that on the 7th, 8th, and 9th of February 

 the specimen was found struggling on the surface of the water and 

 had to be removed therefrom and placed on the dry surface of the 

 aquarium — thus probably shortening its life — it lived until the evening 

 of February 1 1, or slightly over eight days. On the 7th of the month 

 eggs were deposited in the water. The form of the mass was tubular, 

 the entire tube being about 12 mm. in length and nearly 2 mm. in 

 diameter. Only the lower 6 mm. of the tube contained eggs, which 

 were arranged in regular circles. The computed number of eggs was 

 slightly over 450. The apex of the tube was attached to a small piece 

 of floating detritus. The eggs were preserved in alcohol four days 

 after they were laid. 



