40 
Journal of A gricultural Research 
Vol. XXV, No. I 
Tabus III .—Mortality of Platygaster vernalis, as observed in collections of Hessian fly 
forms made at intervals during the years 1918, 1919, IQ20, and 1921 — Continued 
1921: EIGHT COLLECTIONS FROM FARM, NEW WINDSOR, MD—Continued. 
Date of collection. 
Fly forms 
examined. 
Results of examination of Hessian fly forms. 
Contain¬ 
ing living 
P. vernalis. 
Contain¬ 
ing dead 
unrecog¬ 
nizable 
matter 
and dead 
P. vernalis. 
Otherwise 
parasitized. 
Living un¬ 
parasitized 
fly forms. 
Mortality 
of 
P. vernalis. 
Number . 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
May 9 . 
T1 7 
76. 07 
15-39 
O. 85 
7.69 
O. OO 
June 3 . 
100 
63.00 
21 . OO 
16. OO 
. OO 
17. 18 
21. 
100 
29. 00 
23. OO 
40. OO 
8. 00 
61.88 
July 12. 
100 
16. 00 
43.00 
38. OO 
3. 00 
78.97 
28. 
100 
16. 00 
56.OO 
26. OO 
2. 00 
78.97 
Aug. 12. 
IIO 
20. 91 
46. 36 
28. 18 
4 - 55 
7 2 - 5 i 
^ 30 . 
100 
21 . OO 
47.00 
29. OO 
3. 00 
7 2 -39 
Sept. 23..... 
100 
6. 00 
70 . OO 
21 . OO 
3.00 
92 . II 
In all cases, for the sake of the uniformity necessary in obtaining 
correct percentage results, the host is taken as the unit. For instance, 
if all the individual parasites in a single host were dead, the latter was 
classified as containing dead vernalis , but if one or more of the vernalis 
were alive, the host was classified as containing the living parasite. 
^ Under the heading “Otherwise parasitized” are included puparia 
from which parasites other than vernalis have emerged, or in which such 
other parasites are recognized whether dead or alive. In case of the re¬ 
cognizable occurrence of both vernalis and some other parasite in the 
