18 



CIRCULAR 4 2 2, U. S. DEPARTMENT OF AGRICULTURE 



In 1932 larvae of the first generation began hatching May 4, and 

 in 1933 on April 30. The maximum and minimum developmental 

 periods for 255 larvae of the first generation were 128 and 39 days, 

 respectively. In 1933 these periods among 917 larvae were 77 and 29 

 days, respectively. The average larval periods of the second gener- 

 ation also were slightly shorter in 1933, when higher temperatures 

 prevailed. As stated previously, however, the variation in the rate 

 of growth of tobacco moth larvae cannot be satisfactorily explained 

 on the basis of temperature and quality of food alone. 



PUPAL PERIOD 



The maximum and minimum pupal periods for the first and second 

 generations in 1932 and 1933 are given in table 5. 



Table 5. — Pupal periods of the tobacco moth in the laboratory, Richmond, Va., 



1932 and 1933 



FIRST GENERATION 





1932 



Period of enter- 

 ing pupation J 



June 27- July 4__ 



July 4-11 



July 11-18 



July 18-25 



July25-Aug. 1__ 



Aug. 1-8 



Aug. 8-15 



Aug. 15-22 



Aug. 22-29 



Aug. 29-Sept. 5__ 



Sept. 5-12 



Sept. 12-19 



Sept. 19-22 



Sept. 20-27 



Sept. 27-0ct. 4_. 

 Oct. 4-8 



Pupae 



Num- 

 ber 

 3 

 19 

 23 

 38 

 28 

 40 

 ' 45 

 22 

 16 

 9 

 5 

 6 

 1 



Length of pupal 

 period 



Range 



Days 

 11-12 

 6-12 

 8-12 

 6-12 

 9-12 

 5-12 

 8-14 

 11-13 

 8-11 

 10-16 

 10-16 

 14-23 

 25 



Weight- 

 ed aver- 



Days 

 11.5 

 10.3 

 10.8 

 10.3 

 10.6 

 10.2 

 11.6 

 11.9 

 9.5 

 12.2 

 13.9 

 17.8 

 25.0 



Aver- 

 age 

 mean 

 temper- 

 ature 



for 

 pupal 

 period 



Period of enter- 

 ing pupation • 



June 8-15 



June 15-22 



June 22-29 



June 29-July 6 



July 6-13 



July 13-20 



July 20-27 



July 27-Aug. 3 



Aug. 3-10 



Aug. 10-14 



Pupae 



Num- 

 ber 

 16 

 24 

 111 

 389 

 206 

 31 

 61 

 27 

 5 

 4 



Length of pupal 

 period 



Range 



Days 

 12-14 

 10-12 

 8-13 

 9-15 

 11-15 

 10-13 

 9-12 

 8-13 

 11-12 

 8-12 



Weight- 

 ed aver- 



Days 

 12.9 



11.1 



10.4 

 11.1 

 12.1 

 11.1 

 10.4 

 11.1 

 11.4 

 10.3 



Aver- 

 age 

 mean 

 temper- 

 ature 



for 

 pupal 

 period 



SECOND GENERATION 



2 



11-14 



12.5 



75 





1 



15 



15.0 



68 





2 



9-25 



17.0 



71 





July 24-31 



July 31-Aug. 7. 



Aug. 7-14 



Aug. 14-21 



Aug. 21-28 



Aug. 28-Sept. 4 



Sept. 4-11 



Sept. 11-17 



1 



10 



10.0 



5 



9-12 



11.1 



16 



9-12 



10.9 



27 



8-14 



11.7 



15 



10-14 



12.5 



9 



10-12 



10.9 



2 



11 



11.0 



1 



15 



15.0 



i Records were made during the day, and those larvae that pupated in the early part of the day were 

 counted with one group and those pupating after the count were included in the following period. 



For the first generation the maximum and minimum pupal periods 

 for 255 pupae in 1932 were 25 and 5 days, respectively. In 1933 the 

 maximum and minimum periods for 874 pupae were 15 and 8 days, 

 respectively (table 5). The shorter periods in 1933 were probably due 

 to the slightly higher temperatures which prevailed. The length of 

 the pupal period increased at lower temperatures and was shortened 

 by high temperatures. 



