RATE OF MULTIPLICATION OF HESSIAN FLY. : 5 
SPRING GENERATION. 
For the spring generation the ova have been counted for 160 
females. The most surprising thing about the results obtained, as 
shown in Table 2, is the general average number of ova per female . 
of 232.9. This is an average of 54 eggs per female less than was 
found im the case of the fall brood. 
TABLE 2.—Average number of ova for females of the spring generation of the 
Hessian fly; counts made at Carlisle, Pa., in the fall of 1919. 
| Number Total Minimum | Maximum Average 
Cage No.— offemales | number per per Range. per 
counted. of ova. female. female. female. 
1S GU aE lh ee Aenea 57 14, 591 79 386 307 256. 0 
DRADER PE aces ese 135521 29 6, 920 113 372 259 241.0 
TSO) NS eS ah Re a 4 780 34 | 297 263 195. 0 
dey Gee Fle SEE 9-4 Se ese Se Te 13 3, 105 188 390 162 238.8 
TRL Ae eR ME a a aor 5 836 71 | 255 184 167.2 
DiS Nat Slee ag Mg a a ee a 8 1,356 102, 214 112 169. 5 
CASSEL ae 6 1,048 100 227 127 | 174.7 
dtl’) 9 IN eB A pe ALIS BY SS a ip ln 2 483 194 289 95 | 241.5 
ESBS P opera eros Sakray Ley AGS 5 8 26 5, 965 116 370 254 | 229. 4 
SC DASE le i ea 10 2, 106 108 309 201 210. 6 
PLOUAISLE Datcmirene St cae 160 37, 260 34 386 352 232.9 
While this work has been carried through only one spring genera- 
tion, it 1s nevertheless quite evident that this generation is con- 
stantly lower than the fall generation in its capacity for egg produc- 
tion. The actual minimum number of ova per female is 34, which 
is one more than for the fall brood. The maximum, 386, on the 
contrary, is much lower, and the range of variation is only 352. 
SUMMER GENERATION. 
While data for the flies developing in volunteer wheat are scant, 
the results obtained seem interesting enough to be included as 
Table 3. Only 15 cases are available.. In spite of the low average 
number of eggs, this brood in all probability resembles rather closely 
the fall generation in the number of eggs it can lay. If this should 
prove true, it might be that the stage of growth of the plant has an 
important relation to the size of the flies developing in a plant, 
and consequently to the number of ova developing. ‘ 
TABLE 3.—Average number of ova for females of the generation of the Hessian 
fly developing in volunteer wheat; counts made at Carlisle, Pa., in the sum- 
mer of 1919. a 
Number Total | Minimum | Maximum Average 
Cage No. offemales | number “per per Range. per 
counted. of ova. female. female. female. 
UES US Re LED fa i a Rae 2 524. 177 347 170 262. 0 
Ie Rey se! Mae tS 13 3, 027 54 448 394 232. 8 
MOvabsry came eae Fe 0 15 3, 551 54 448 | 394 236. 7 
