36 



MASS. EXPERIMENT STATION BULLETIN 189. 



Table VIII. — Duration of Incubation Period — Second Generation — Con. 



229, 

 230, 

 231, 

 232, 

 2o3, 

 234. 

 235, 

 236, 

 237, 

 238, 

 239, 

 240, 

 241, 

 242, 

 243, 

 244, 

 245, 

 246, 

 247, 

 248, 

 249, 

 250, 

 251, 

 252. 

 253, 

 254, 



Observation Numbeb. 



Number ( 

 Eggs. 



Deposi- Hatch- 

 tion, 1918. ing, 1918. 



Aug. 11 

 Aug. 12 

 Aug. 13 

 Aug. 14 

 Aug. 15 

 Aug. 22 

 Aug. 23 

 Aug. 23 

 Aug. 23 

 Aug. 24 

 Aug. 24 

 Aug. 24 

 Aug. 25 

 Aug. 25 

 Aug. 25 

 Aug. 26 

 Aug. 26 

 Aug. 26 

 Aug. 26 

 Aug. 26 

 Aug. 27 

 Aug. 27 

 Aug. 27 

 Aug. 27 

 Aug. 27 

 Aug. 29 



Aug. 17 

 Aug. 17 

 Aug. 19 

 Aug. 22 

 Aug. 23 

 Aug. 27 

 Aug. 29 

 Aug. 29 

 Aug. 29 

 Aug. 30 

 Aug. 31 

 Aug. 30 

 Aug. 30 

 Sept. 1 

 Sept. 1 

 Sept. 3 

 Sept. 3 

 Sept. 3 

 Sept. 3 

 Sept. 3 

 Sept. 4 

 Sept. 4 

 Sept. 4 

 Sept. 4 

 Sept. 4 

 Sept. 6 



Duration of 



Incuba- 

 tion Period 

 in Days. 



Average duration of incubation period, 6.13 days. 



Maximum duration of incubation period, 8 days. 



Minimum duration of incubation period, 4 days. 



In the course of their development the larvse of the second generation 

 feed in a manner similar to that described for the first generation. They 

 pass through four or five instars before the advent of severe winter weather, 

 which halts their activities and indefinitely prolongs the duration of the 

 last instar or instars. According to data secured from 25 larvae, reared 

 in life-history cages from eggs to the time when their activities ceased, 

 the average duration of the first instar was 5.4 days; second instar, 4.2 

 days; third instar, 5 days; fourth instar, 9 days; and fifth instar, 10 

 days. The average duration of the total larval period was 26 days, with 



