BIOLOGY OF TOBACCO MOTH AND ITS CONTROL 



19 



LENGTH OF LIFE CYCLE 



The egg-to-adult period of the tobacco moth showed a wide range, 

 which was due for the most part to the uneven rate of growth of the 

 larvae. The maximum and minimum periods for individuals of the 

 first and second generations which completed growth in 1932 and 1933 



are given in table 6. 



Table 6. — Egg-to-adult jieriods of the tobacco moth in the laboratory, Richmond* 



Va., 1932 and 1933 



FIRST GENERATION 



1933 



1932 







Length of egg-to- 



Averege 







adult period 



mean 





Adults 







temper- 

 ature 



Period eggs were 







laidi 



duced 





Weight- 



for de- 

 velop- 

 mental 







Range 



ed aver- 









age 



period 





Number 



Days 



Days 



°F. 



Apr. 22-29 



16 



82-123 



94.6 



56 



Apr. 29-May 6.. 



10 



81-152 



102.7 



70 



May6-13 



151 



58-144 



93.9 



74 



May 13-20 



26 



66-151 



102.7 



70 



May 20-27 



42 



63-134 



88.2 



72 



May 27- June 2.. 



10 



59-133 



79.0 



73 





Adults 

 pro- 

 duced 



Length of egg-to- 

 adult period 



Period eggs were 

 laid i 



Range 



Weight- 

 ed aver- 

 age 



Apr. 18-25 



Apr. 25-May 2-. 



May2-9 



May9-16 



May 16-23 



May 23-30 



Number 



26 



88 



311 



99 



275 











95 



Days 

 62-123 

 55-97 

 52-93 

 50-93 

 46-77 



Days 

 71.3 

 75.6 

 70.3 

 65.9 

 59.4 



May 30- June 6__ 







June 6-13 



49-75 



60.3 



Average 



temper- 

 ature 

 for de- 

 velop- 

 mental 

 period 



■F. 



SECOND GENERATION 



Aug. 9-14. 



54-79 



64.0 



83 



June 25- July 1. 



Julyl-8 



July 8-15 



July 15-16 



5 



39-53 



47.6 



32 



40-63 



47.5 



46 



44-85 



54.3 



1 



62 



62.0 



i Records were made during the day, and those eggs that were laid in the early part of the da y were counted 

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



The rearings included in table 6 were exposed to higher tempera- 

 tures in 1933, and this is in part responsible for more rapid develop- 

 ment than shown in those of 1932. The maximum and minimum de- 

 velopmental periods of 255 moths of the first generation in 1932 were 

 152 and 58 days, respectively. In 1933 the range for 894 moths was 

 from 123 to 46 days. This more rapid growth in 1933 allowed 84 

 moths of the second generation to be reared, whereas in 1932 only 5 

 second-generation moths completed development. The lowest average 

 egg-to-adult period, 47.5 days, for a group was for 32 moths that 

 hatched during the interval July 1 to 8, 1933. 



Observations made in tobacco storage warehouses in Virginia and 

 North Carolina showed that the life cycle of the moth was approxi- 

 mately the same as in the laboratory. Spring emergence began usu- 

 ally from 7 to 10 days later in warehouses, owing to the longer time 

 required for the temperature of bales and hogsheads of stored to- 

 bacco to rise. This lag in seasonal occurrence between laboratory 

 and storage-reared moths is equalized in the fall, since the tempera- 

 ture of bales and hogsheads drops more slowly than the temperature 

 of laboratory rearing containers. 



