THE PARASITES OF POPILLIA JAPONICA 
39 
during the attempted second oviposit ion. The grub having once 
borne an egg in the preferred crevice, or one on each side, is there- 
after oviposited upon at a different point, either immediately in 
front of or behind that position. Where egg laying over a consider- 
able period is confined to a single grub and the host then examined, 
it is found to bear a pair of oviposition scars on each intersegmental 
crevice from the first to the last on the abdomen, and only a single 
egg usually remains, this being the one last laid. 
The grubs most preferred by Tiphia for oviposition are those in 
the early or middle third stage, for after they pass to the more mature 
form the body becomes thickened and firm, and thus apparently 
presents mechanical difficulties to stinging and egg laying. Such 
grubs are from eggs laid the previous season, and it was only with 
great difficulty that wasps were induced to oviposit upon them. 
In the field during early September the grubs from eggs of that season 
were largely in the second instar, and collected grubs of this stage 
often bore Tiphia eggs and larvae. Manifestly, grubs in this stage 
were unable to provide sufficient food to bring the parasite larvae 
to maturity, and in many cases observed the resulting cocoons were 
little larger than those of an average-sized Apanteles. The larvae 
in these cocoons usually die shortly after the formation of the cocoon . 
This willingness of the species to oviposit upon grubs of too small 
size to bring its progeny to maturity indicates a lack of perfect 
adaptation to a one-year cycle of the host, because of the improper 
time of emergence for a wasp of this size. 
The rate and duration of oviposition in this species were deter- 
mined in a series of 28 females collected in the field on August 19, 
which was very nearly the first date upon which adults appeared, 
and consequently it is reasonably certain that little or no egg laying 
had taken place up to that time. Records of the 10 best females 
are given in Table 2, and this is felt to represent very nearly the 
normal condition in the field. 
Table 
2 — 
-Oviposition r 
ecords < 
)/ 10 females 
of 
Tiphia popi.liavora 
Female 
August 
September 
Total 
No. 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
1. 
3 
1 

1 
1 
2 
1 

3 
2 
1 


1 
1 
1 

1 
2 


1 
1 
1 

1 
2 
1 
3 
1 

1 
2 
2 
1 
2 
2 

2 
2 
2 
1 
2 
1 

1 
2 
4 
2 
2 
1 
2 
3 
1 
1 
3 
2 
3 
3 
2 
2 

1 
1 

3 
2 
3 
1 
2 
2 
2 
2 
1 
2 
2 
2 
2 
2 
2 
2 
1 
2 
1 
2 
2 
2 
2 
3 
3 
2 
3 
3 
2 
1 
1 
2 
2 
3 
3 
3 
2 
2 
3 
3 
4 
3 
3 
1 
3 
2 
2 
2 
2 
3 
1 
2 
3 
2 
3 
2 
1 
2 
2 
2 
2 
3 
3 
1 
2 
1 
3 
2 
2 
I 
2 
3 
2 
2 
2 
2 
3 
1 
5 
3 
2 
3 
3 
3 
1 
2 
1 
4 

2 
4 
2 
2 
2 
2 
2 
2 
2 
2 
3 
2 
1 
1 
4 
3 
2 
47 
9 
34 
3 
30 
4 
3 
2 
2 
3 
39 
5 
6 
1 
2 
38 
32 
3 
6 
1 
1 
2 
3 
32 
8 
33 
9. 
38 
10 
1 1 
2 
37 
Average 
36 
! 
It will be seen from these records that the general average per 
day was approximately 2, with a maximum of 6. In the laboratory, 
under forcing conditions in capsules as previously mentioned, as 
many as 8 eggs were obtained within a period of 6 hours, but this was 
abnormal and is not duplicated in the field. 
