100 Swede Midge in parts of Yorkshire 



APPENDIX. 



1913 and 1914. Dates of surveys and tests of accuracy of surveys. 



1913 Brood I. 

 July 9—31. 



One field at Driffield repeated. 



Survey, July 16 and 18, in two rows, 354 infected plants. 



Repeated, Aug. 6, in same two rows, 374 infected plants. 



1913 Brood II. 

 Aug. 12— Sept. 12. 



Six fields repeated in Districts III and IV. 



Survey, Aug. 14—20, % CL, 0-25, 2-5, 0-7, 4-5, 3-5, 10. 



Repeated, Sept. 9, fields in same order, % CL, 0-25, 2-5, 1-25, 5-0 4-0, 2-0. 



This I believe to be the least accurate of my five surveys. 



1914 Brood I. 

 July 7—26. 



Two fields repeated. 



A, in District VII. Survey, July 10, in three rows, 241 infected plants. 



Repeated July 26, in same three rows, 214 infected plants. 



B, in District IX. Survey proper, July 15, in two rows, 95 infected plants. 



Repeated, July 26, in same two rows, 95 infected plants. 



1914 Brood II. 

 Aug. 17—28. 



Seven fields repeated in District V. 



Survey, Aug. 18, % CL, 6, 9, 10, 14. 13, 10, 8. 



Repeated, Aug. 28 and 29, fields in same order, % CL, 9, 12, 10, 14, 8, 11, 9. 



1914 Brood 111. 

 Sept. 22— Oct. 4. 

 Eight fields repeated in District V. 



Survey, Sept. 22, % CL, 23, 15, 15, 21, 12, 19, 13, l(i. 



Repeated, Oct. 4, fields in same order, in same rows as in survey proper, % CL, 18, 

 21, 13, 19, 10, 18, 13, 13. 



There was no danger of more than very slight inaccuracy in each of the Brood I 

 surveys from more Brood I flies coming out after the survey began, for each year 

 the Brood I maggots had to a large extent left the plants before the Brood I survey 

 began. 



In the Brood II test fields, in both years, neighbouring rows to those examined 

 in the survey were selected, not the actual rows examined in the survey, because 

 in examining a plant at the time when infected leaves were small before deciding 

 \\ lnther it was attacked or not I had sometimes destroyed the signs of attack. In 

 the other surveys I was able to avoid doing this in the fields which I afterwards 

 repeated as tests. 



