4 BULLETIN 1008, U. S. DEPARTMENT OF AGRICULTURE. 
for males which are sure to emerge. Taking all of these facts into 
consideration, success beyond expectations was achieved in the fail 
of-1919, in making counts for the spring brood of 1920.° 
AVERAGE NUMBER OF OVA FOR THE PRINCIPAL BROODS. 
In presenting the results of this investigation, it will be necessary 
to consider first the average number of ova which can be laid by 
females of the principal generations. The data for each of these 
generations will be tabulated separately. After this has been done, 
it will be necessary to take into consideration the proportion of the 
two sexes before a sufficient basis can be had for estimating the rate 
of reproduction of the Hessian fly. 
FALL GENERATION. 
In Table 1 are given the results of counting the number of ova 
contained in 107 females. These flies were obtained from six dif- 
ferent fields, as indicated by their cage numbers. It will be noted 
that the average number of eggs per female varies considerably in 
different fields, even when the number of females counted is approxi- 
mately the same. It is thus easy to see what a difficult matter it is 
to obtain a fair average number of eggs per female. The figures, 
however, are as fair as could be obiaaned for the year in question 
and in the time available. | 
TABLE 1.—Average number of ova for “females: of the fall generation of the 
Hessian fly, Carlisle, Pa., 1919. 
| | l | be peugeot 
Number | wmber piace Maximum | | Average 
Cage No.+ | oi females anos per per Range. | per 
| counted. | * | female. | female. | | female. 
| | 
NG) eee eee a we ee ES oe 28 | 8, 014 74 383 309 | 286. 0 
APEGS stesso eh teh 26 6, 148 33 365 |. 332 | 236. 2 
Uy SS Eee a eat nea ee Bel eee 36 13, 422 189 464 275 372.8 
WIGS 2 Bee ie ee bed oe ot 9 1,361 107 195 88 151.2 
Oe oe Boe a 2 set esos wis S28: 6 1,099 134 302 168 183.2 
AVOS ASE. ARE. Lp e332. 2 658 314 344 30 | 329.0 
Pdtatsee oe 0 1) | 107 30, 702 33 464 | 431 |, 286.9 
H | ae | 
The actual number of ova per female varies from 33 to 464, with 
a range of variation of 431 and an average per female of 286.9. 
It may be added that the smallest female found since this work 
_began belonged to this brood, but to none of the foregoing cage 
numbers. This female was dissected by Mr. Hill, who found that 
it contained only 11 ova. The largest female ever found belonged 
also to this brood. This female was in a different series and con- 
tained 474 ova. 
‘In this connection the writer wishes to state that two lots of females of the fall 
brood were dissected by Mr. C. C. Hill; Mr..P. R. Myers has determined the sex of a 
large proportion of the flies as they emerged, and both men have helped in collecting 
and caging the material. All of the work has been done in the laboratory at Carlisle, 
Pa., and most of the material has been collected near by. 
