14 



BULLETIN 911, U. S. DEPARTMENT OF AGRICULTURE. 



The data from Table XVII are summarized in Table XVIII. The 

 average length of the prepupal period was 1.77 days, the maximum 

 period 3 days, and the minimum 1 day, where unsprayed foliage was 

 supplied. Where the cocoons were formed on sprayed foliage the 

 average prepupal period was 2.9 days, the maximum 5 days, and 

 the minimum 1 day. The spray material apparently had a repellent 

 action, for in another experiment where both sprayed and unsprayed 

 foliage were equally accessible to larvse there were 226, or 63 per 

 cent, of the total number of cocoons formed on unsprayed leaves and 

 but 135, or 37 per cent, formed on sprayed leaves. Considerable 

 mortality can be attributed to cocooning on sprayed leaves, since 

 194 pupse were formed in 223 cocoons on unsprayed leaves, a mor- 

 tality of 13 per cent as compared with the individuals that cocooned 

 on sprayed leaves, where but 37 pupse were formed in 64 cocoons, 

 showing a mortality of 42 per cent. 



TIME OF COCOONING OF FIRST-BROOD LARV^. 



Table XIX. — Time of cocooning of '2,447 larvse of the first brood of the grape-berry moth, 



Sandusky, Ohio, 1917. 



Date of cocooning. 



July 19 

 July 20 

 July 21 

 July 22 

 July 23 

 July 24 

 July 25 

 July 26 

 July 27 

 July 28 

 July 29 

 July 30 

 July 31 

 Aug. 1. 

 Aug. 2. 

 Aug. 3. 

 Aug. 4. 

 Aug. 5. 

 Aug. 6. 

 Aug. 7. 

 Aug. 8. 

 Aug. 9. 

 Aug. 10 

 Aug. 11 

 Aug. 12 

 Aug. 13 



Number 



of 

 cocoons. 



Mean 

 daily 



temper- 

 ature. 





°F. 



3 



71 



2 



76 



9 



76 



9 



76 



18 



78 



10 



80 



31 



78 



44 



80 



55 



76 



73 



72 



54 



86 



128 



87 



170 



88 



129 



88 



142 



74 



230 



71 



117 



68 



112 



80 



131 



76 



158 



76 



111 



75 



26 



66 



64 



66 



37 



68 



62 



71 



45 



74 



Date of cocooning. 



Aug. 14 



Aug. 15 



Aug. 16.... 

 Aug. 17. . . . 

 Aug. 18.... 

 Aug. 19. . . . 

 Aug. 20. . . . 

 Aug. 21.... 

 Aug. 22. . . . 

 Aug. 23. . . . 

 Aug. 24. . . . 



Aug. 25 



Aug. 26 



Aug. 27. . . . 

 Aug. 28. . . . 

 Aug. 29. . . . 

 Aug. 30. . . . 

 Aug. 31.... 



Sept. 1 



Sept. 2 



Sept. 3 



Sept. 6 



Sept. 8.... 



Total 



Number 



of 

 cocoons. 



Mean 

 daily 

 temper- 

 ature. 



74 

 72 

 74 

 68 

 68- 

 73 

 78 

 73 

 72 

 72 

 66 

 60 

 62 

 73 

 68 

 62 

 64 

 64 

 75 

 69 

 67 

 66 

 62 



In Table XIX are given the complete records of cocooning for the 

 first-brood larvse. Cocooning began on July 19 and continued until 

 September 8 with a distinctly high period from July 30 until August 8. 

 The correlation with temperature is of interest, showing that as the 

 mean temperature dropped below 70° F. there was a drop in the rate 

 of cocooning. 



