THE IMPORTED PIXE SAWFLY. 
15 
Table S. — Effect of time of year and temperature on rate of development of the egg and 
larval instars of Diprion simile. 
Stage. 
Earlier colony. 
Date 
stage or 
instar 
began. 
Average 
Time in tempera- 
stage or j ture in 
instar. stage or 
j instar. 
Later colony. 
Date 
stage or 
instar 
began. 
Average 
Time in \ tempera- 
stage or j ture in 
instar. \ stage or 
instar. 
1916 
June 24 
Days. 
7 
July l 
4 

10 
12 
15 
V. 
o 
2 
3 
2 
7 
1916 
Egg May 9 
Larval instar: 
1 22 
II 29 
III ; June 2 
IV 6 
V 12 
VI 17 
Prepupa 29 
Total 
Days. 
F. 
61.61 
6S.7S 
64.50 
66.25 
64.33 
67.90 
70.46 
2i 
30 
F. 
72.85 
71.25 
72.70 
77. 75 
79.00 
75.25 
76.28 
74.51 
Some scattered observations record the larva? feeding close to the 
trunk on a cool and rainy day (temperature 60° F., humidity 87 per 
cent) , feeding vigorously and spread out on a warmer and less humid 
day (temperature 69° F., and humidity 68 per cent), and clustered 
on needles close to the bole on a still warmer and drier day (tempera- 
ture 85° F.j humidity 40 per cent). These observations would seem 
to indicate a rather low optimum temperature, somewhere between 
69° and 85° F., with a rather delicate responsiveness to any consider- 
able variation in* temperature, and the fact that the larvae were 
observed to be rather slow in developing during a damp period and 
inactive during a cool, rainy spell (temperature 56° to 71° F. and 
humidity 85 per cent) tends to show a similar sensitiveness to humid- 
ity. The observations, however, are too few and were made in too 
restricted an area to be of much value. 
PARTHENOGENESIS. 
Diprion simile can reproduce parthenogenetically; that is, eggs 
laid by virgin females are fertile and hatch, producing larvae which 
grow, become prepupa?, spin cocoons, and finally emerge as adults. 
All the adults thus far obtained from eggs of unfertilized females, 
however, are males, a result believed usual for parthenogenetic 
reproduction in sawflies. 
Females that have not mated appear to wait two days before com- 
mencing oviposition, as shown in Table 3, but after this period passes 
they begin to lay unfertilized eggs. Two of the experiments per- 
formed to obtain these unfertilized eggs were successful, one female 
laying 53 eggs, the other 27. A comparison of the number of eggs 
laid parthenogenetically with the number laid by a normal fertilized 
female indicates that the virgin female lays only half as many egirs as 
the fertilized female. In the two parthenogenetic experiments in 
which eggs were deposited about 72J per cent of the eggs hatched, 
which is approximately the same as the percentage of hatching 
obtained from eggs of fertilized females. The mortality among the 
