24 



THE GRAPE ROOT-WORM. 



first beetle emerged July 1, which shows a fairly uniform emergence 

 of beetles in captivity as compared with their emergence in the field. 

 The results of the emergence experiments are given in Table I. 



Table I. — Date of the emergence of 898 grape root-worm beetles (Fidia viticida) from 

 the ground, as observed in the breeding cages in the spring and early part of the summer 

 of 1909 at North East, Pa. 



Date. 



Number 

 of beetles. 



Date. 



Number 

 of beetles. 



Date. 



Number 

 of beetles. 



Date. 



Number 

 of beetles. 



Julyl 



July 2 



July 3 



July 4 



Julys 



July 6 



July 7 



Julys 



5 

 9 



16 

 11 

 15 

 27 

 34 

 31 



July9 



July 10. . . . 

 July 11.... 

 July 12. . . . 

 July 13.... 

 July 14. . . . 

 July 15. . . . 

 July 16.... 



36 

 39 

 19 

 36 

 22 

 16 

 26 

 14 



July 17. . . . 

 July 18. . . . 

 July 19. . . . 

 July 20. . . . 

 July 22. . . . 

 July 23.... 

 July 24. . . . 

 July 25. . . . 



8 

 4 

 5 

 2 

 6 

 1 

 5 

 2 



July 27. . . . 

 July 29. . . . 

 July 30. . . . 

 Aug. 5..., 

 Aug. 9.... 



4 



1 

 2 



1 

 1 







1 





Total . . 



148 



Total.. 208 



Total.. 



33 



Total.. 9 



In figure 13 the curve shows more graphically the relative emer- 

 gence of these beetles. It will be noted from this curve that after 



Fig, 13,— Curve showing time and relative emergence of beetles of the grape root-worm from the 

 ground in rearing cages at North East, Pa., 1909. (Original.) 



the first emergence the beetles continued to appear in rapidly increas- 

 ing numbers, reaching a maximum July 10. The decrease in the 

 number of beetles emerging after this date was more gradual, and 

 emergence continued until late in the season. In the cages the last 

 beetle emerged August 9, while in the field a single beetle was still 

 found in the cell August 14. From July 1 to July 5, inclusive, 14.1 

 per cent had emerged; from July 6 to July 16, 75.4 per cent had 

 emerged; and the remaining 10.5 per cent emerged later. Thus the 

 great majority of over 75 per cent emerged during a period of 10 days, 

 and the maximum of emergence took place about 2 weeks after the 

 first beetle had been observed in the field. 



