16 MASS. EXPERIMENT STATION BULLETIN 352 



to hatch; but when 20 eggs were placed in a root cellar where the temperature 

 was 60° to 70° F., maggots hatched from all of them in 12 and 13 days. In 1932, 

 eggs were placed in constant-temperature cabinets operated at 55°, 65°, 75°, 

 and 85° F. In these cabinets all of the eggs died at 85° F., and the 65° F. tempera- 

 ture appeared most favorable. 



Table 15. Incubation of carrot rust fly eggs at constant temperature 

 First Generation, Waltham, Mass. 1932. 



Feeding of Larvae 



The time required for the feeding and development of the larvae in the carrots 

 was approximately 4 weeks, the average period in the three years when studies 

 were made varying from 27.5 to 30.1 days. This feeding period of the first genera- 

 tion larvae generally occurs from the middle of June to the middle of July, but 

 it may begin June 1 and extend to August 1. 



When the maggots have completed their growth in the carrot, they enter the 

 soil within 1 or 2 inches of the root in which they were feeding and form a small 

 cell about 4 inches beneath the surface. 



During the first 3 days in the soil the maggots make preparations for the pupal 

 period. In 1928 the time in the soil averaged 30.8 days, but in 1930 this period 

 was 41.44 days. In 1930 there appeared to be two groups, one of which spent 

 7 weeks in the soil while the other spent about 4 weeks in the soil. Although 

 there is no definite proof regarding the cause of this variation, it is apparently 

 connected with drought or temperature and indicates the ability of these pupae 

 to survive unfavorable conditions. 



Table 16. Feeding of carrot rust fly larvae in carrots 

 First Generation, Waltham, Mass. 1928-1930. 



