10 CIRCULAR 269, IT. S. DEPT. OF AGRICULTURE 



LARVAL PERIOD 



The developmental periods of larvae reared on flue-cured tobacco 

 are given in Tables 1 and 2. The periods shown in Table 1 ranged 

 from 29 to 72 days. These larvae showed an uneven rate of growth 

 despite the fact that they were all provided with the same quality 

 of tobacco and handled in a similar manner. Temperature is un- 

 doubtedly a very vital factor in the growth of the larvae, although 

 some individuals developed very slowly during hot summer weather. 

 Larva No. 25 (Table 1) required 29 days to complete its growth, at a 

 mean temperature of 81.2° F.; whereas larva No. 30 required 72 days, 

 at a mean temperature of 75.3°. Owing to this uneven rate of growth, 

 it is difficult to draw conclusions as to the effects of temperature. 

 The larval periods of the individuals shown in Table 2 ranged from 

 35 to 54 days. Here again the rate of growth was uneven. For 

 example, larva No. 4 (Table 2) required 35 days for the larval period, 

 and larva No. 15 required 48 days. These larvae hatched on August 

 17 and were exposed to similar conditions in the laboratory. 



PUPAL PERIOD 



The pupal periods shown in Table 1 occurred during August and 

 September, when summer temperatures prevailed, the average period 

 being 11.3 days. The shortest period was 7 days, at a mean tempera- 

 ture of 81.6° F. and the longest 19 days, at a mean temperature of 

 63.3°. The periods shown in Table 2 ranged from 12 days, at a mean 

 temperature of 58.2°, to 24 days, at a mean temperature of 57°. The 

 pupal periods shown in Table 2 occurred during October and Novem- 

 ber, the average for the 30 pupae being 16.7 days. Most of the larvae 

 pupated in loosely woven cocoons near the surface of the tobacco in 

 which they were reared. 



EGG-TO-ADULT PERIOD 



There is a wide variation between the shortest and the longest egg- 

 to-adult period, as shown in Tables 1 and 2. In Table 1 rearings Nos. 

 8, 12, and 13 completed the cycle in 45 days, at mean temperatures 

 of 80°, 80°, and 80.2° F., respectively. Rearing No. 30 required 95 

 days to complete the cycle, at a mean temperature of 73.3°. 



In Table 2 rearings Nos. 4, 16, and 17 completed growth in 56 days, 

 when the mean temperatures were 76.5°, 77°, and 77° F., respectively. 

 The longest period in Table 2 (that required in rearing No. 28) was 

 81 days, at a mean temperature of 73.3°. The length of the egg-to- 

 adult period is influenced by temperature. During hot weather most 

 individuals have a more rapid growth. It was observed, however, 

 that there are larvae upon which temperature appears to have little 

 effect. As an illustration, rearing No. 30 (shown in Table 1) hatched 

 July 22 but did not complete its cycle until October 21. 



DATA ON MATED MOTHS 



During July, August, and September, 1931, females of Ephestia 

 elutella were mated on the day they emerged. Data concerning these 

 moths are given in Table 3. All the females listed in Table 3 were 

 mated on the date of their emergence. Each pair of moths was seg- 

 regated in a glass vial and given a small piece of flue-cured tobacco 

 leaf. The tobacco was replaced by a fresh piece every 24 hours, and 

 the eggs laid during this interval were counted. It was observed that 



