460 



Journal of Agricultural Research voi. xvni. No. 9 



Table I. — Emergence of winter brood of Oscinis frit 



Date of emergence, o 



Cage No. 2, 



caged 



Mar. 30. 



Cage No. 3, 



caged 



Mar. 30. 



Cage No. 4, 



caged 



Apr. II. 



Cage No. 5, 



caged 



Apr. II. 



Total by 

 days. 



Apr. 26 



29 



30 



May 3 



6 



9 



15 



19 



25 



T 31 



June 12 



Total by cages 



o 



5 

 10 



9 



4 

 3 

 o 



6 



18 



13 

 6 



5 

 o 



I 



31 



50 



o Dates on which no observations were made are not entered in the table. . 



From Table I it appears that emergence in 191 6 extended over a period 

 of 29 days (April 26 to May 25) and that 85 per cent of the flies emerged 

 in II days, from April 30 to May 10. It would appear, however, that 

 these dates were retarded by keeping the cages too much in the shade, 

 since sweepings made outdoors at frequent intervals in early April 

 gave the first adult for 191 6 on April 13 and for 191 5 on April 14. 



SUMMER BROODS 



Four complete summer broods were reared in 1916, as reported in 

 Table II. Each cage was started at the time indicated by the cross, 

 using flies that had emerged a few days before. Cages 23, 24, and 26 

 were exceptions, being stocked with garden wheat already heavily in- 

 fested outdoors. This explains their large yield of flies. The wheat in 

 cage 26 was taken up so late (June 16) that there was a possibility of its 

 containing eggs of the second brood; and this probably accounts for 

 the single fly which emerged in it on July 28, 16 days after the last pre- 

 ceding one. The negative observations for each cage are omitted up to 

 the first positive one, after that both positive and negative are included 

 up to the time that the use of the cage was discontinued. All cages that 

 produced no positive results are omitted; they were more numerous 

 than those included. 



Flies of the first summer brood began to emerge on June 12 and con- 

 tinued to do so until July 13 (32 days), the heaviest emergence being 

 from June 25 to 30. 



Flies of the second summer brood began to emerge July 16 and con- 

 tinued to do so until July 26 (only 11 days). Flies emerged in 10 cages. 

 July 2 1 gave the largest record. 



Flies of the third summer brood emerged from August 10 to August 28 

 in 5 cages, a total/ however, of only 21 flies. 



