236 



Journal of Agricultural Research 



Vol. XVI. No. 9 



those issuing from puparia in captivity laid in four or five days. This 

 checks with condition in the field, for the first eggs were observed out- 

 side on May 7. The larvae matured in from 9 to 16 days. Toward the 

 end of the larval period they mined rapidly, producing conspicuous 

 blotches on the leaves. The maturing of the first-generation larvae 

 could thus be easily distinguished. After this it was impossible to fol- 

 low the number of generations by observation in the field alone. One 

 can go out in the field any time during the summer and find eggs, larvae, 

 puparia, and adults all at the same time. 



From a number of eggs laid in the spring by the females, overwinter- 

 ing as puparia, the writer succieeded in rearing adults of the first genera- 

 tion. These adults laid a few eggs, but none of them hatched. By 

 bringing in eggs from the field at this time the writer reared adults 

 of the second generation. This was continued through the summer, 

 and a fair idea of the number of generations was obtained. During 

 1915 and 1916 the writer obtained three and a partial fourth generation. 

 The majority of the fourth generation were overtaken by cold weather 

 and perished. 



From Table IV it will be seen that some of the puparia fonned in 

 June and July, as well as those formed in September, did not give forth 

 adults the same year that they were formed, but overwintered as puparia, 

 and the adults issued the following spring. This seems to be a provi- 

 sion of nature to insure the continuation of the race the following year 

 in case all the individuals of any generation should perish. 



Table IV. — Length of the pupal stage of Pegomyia calyptrata 



Experiment No. 



A150. 

 A168. 



A165. 



A9... 



A14. . 



A167. 

 A169. 

 A182. 



A17.. 



A27. . 



A26.. 



A28. 



A31. 



I,ength of 

 stage. 



Days. 



26 

 26 



27 

 22 

 24 

 25 

 22 



23 

 20 



21 



317 

 20 

 20 



18 

 20 



284 



o Adults issued the following year from puparia kept out of doors over tHe winter. 



