THE IMPORTED PIXE SAWFLY. 
11 
Table 3 shows the length of time elapsing between the emergence 
of the adult and oviposition. 
Table 3. — Preoviposition period of adults of Diprion simile. 
No. 
Date ^ate 
adult 0V t 1 i P° sl " 
emerged., ^ 
Time in 
days from 
emer- 
gence to 
oviposi- 
tion. 
Host plant. 
Remarks. 
3... 
4... 
Mav S. . . 
May 11.. 
May 12. . 
Mav 8... 
Mav 9. . . 
June 20. . 
May 9. . . 
May 11.. 
May 16. . 
May 10. . 
May 11.. 
June 23.. 
Pinus sylvestris. 
do 
Pinus austriaca. 
Pinus svlvestris. 
do 
do 
. Host plant unfavorable, 
. Unfertilized female, 
. Do. 
. ; New needles attractive. 
From the consideration of all the available data the writer is of 
the opinion that a fertilized female will begin laying eggs soon after 
fertilization, provided material suitable for oviposition can be found. 
Such was the case with the first and second females in Table 3. 
Unfertilized females will begin laying after a two-day period during 
which they await mating, provided that suitable material is con- 
venient, as shown by the fourth and fifth females, which were used 
in experiments on partheno^enetic reproduction. A period of longer 
than two days presumably indicates an unfavorable host, unfavor- 
able condition of host, or other disturbing factor. In the instance 
of female Xo. 3, the four-day delay is believed to indicate that Pinus 
austriaca is an unfavorable host, a conclusion borne out by other 
observations discussed under "Hosts." In the instance of female 
Xo. 6, the three-day delay is believed to have been caused by the 
advanced condition of the young needles, which, though not of 
sufficient size for successful oviposition, were yet large enough to 
attract her and thus lengthen the time between emergence and 
oviposition. 
FERTILITY AND INCUBATION. 
In only one of the experiments was an accurate record of the eggs 
from laying to hatching kept, and here it was found that 48 eggs out 
of 69, or 69.5 per cent, hatched. The period of time elapsing between 
oviposition. and hatching is called the incubation period. Table 4 
records the results of investigations to determine the length of this 
period. 
Table 4. — Incubation period of Diprion simile. 
Date laid. 
Date hatched. 
Length 
of 
period. i 
Host. 
Remarks. 
May 9 to 15 May 22 to 26. 
May 10 May22 
May 11 to 15 May 25 to 29. 
Do do 
May 16 Mav 29 
June 23 to 24 j July 1 to 2... 
Days. 
11-13 
12 
14 
14 
13 
Pinus sylvestris. 
do 
do 
do 
Pinus austriaca . 
Pinus sylvestris. 
Unfertilized f emalo . 
Do. 
1 In counting the number of davs in the incubation period, it was assumed that the first eggs laid were the 
first to hatch and that the latest laid were the latest hatched. 
