PROGEESS EEPOET ON THE EUROPEAN CORN BOREE 
87 
Table 24. — Duration of stages of Pyrausta nuoilalis in New England 
{Arlington, Mass.), 1919 to 1921, iiiclusive 
1919 
1920 
1921 
First gen- 
eration 
Second gen- 
eration 
First gen- 
eration 
Second gen- 
eration 
First gen- 
eration 
Second gen- 
eration 
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5 a 
Egg stage. 
7.14 
4.98 
4.70 
4.84 
7.50 
13.10 
12.70 
11.00 
2,990 
7.84 
6,087 
7.16 
4.50 
4.70 
4.00 
6.90 
13.80 
12.20 
4,600 
6.25 
4,992 
7.00 
4, 053 
7.31 
20. 727 
Larval period: 
First instar 
154 
152 
151 
147 
1113 
40 
8 
6. 76 30 
5. 44 30 
7. 86 30 
8. 83! 1 30 
15. 30! 7 
25.00 2 
59 
59 
59 
59 
156 
5 
5.60 
5.90 
9.30 
12.10 
14.40 
16.00 
18 
18 
18 
118 
7 
1 
5.54 
5.40 
5.48 
4.18 
9.50 
24 
24 
23 
22 
4.00 
5.20 
5.20 
6.49 
87 
Second instar _ . 
87 
Third instar . ... 
87 
Fourth instar . . 
87 
Fifth instar... . . . 
21 
..-- , 
Total larva] period 2 \ 
35. 12 
to 
58.82 
H 
197 
244 
2 28.89 
to 
69.19 
H 
33.90 
to 
46.10 
11.04 
11.92 
] [J232.90 
... to 
J I 63.30 
b 
30.10 
61 
54 
120. 89 
Pupal period: 
9 
10.94 
12.61 
18.76 
20.41 
103 
118 
91 
71 
19.14 
20.71 
28 
23 
9.86 
9.24 
18.12 
19.04 
114 
e 
126 
Adult stages: 
Preoviposition 
4.30 
11.80 
3.20 
109 
109 
109 
5.10 
14.10 
120 
1?0 
3.20 
9.50 
93 
93 
4.10 
10.60 
3.80 
18.50 
21.10 
17 
17 
17 
17 
16 
2.60 
13.00 
2.60 
18.20 
17.10 
42 
42 
42 
42 
46 
4.60 
6.80 
4.50 
15.90 
16. 00 
21 
Oviposition... . 
21 
Postoviposition. . 
1. 50| 120 
20. 70 120 
1. 70, 93 
14. 40 93 
15. 20 83 
21 
Longevity? 
19. 30 109 
21 
Longevity J ... 
20.20 
102 
19.50 
110 
21 
Total period from egg tof 
egg ... < 
57.60 
to 
81.20 
I 
| 
55.30 
to 
67. ro 
1 
49.56 
1 
t 
1 
1 The duration of the total larval period varied because a majority of individuals 
pupated (in the first g/eneraton) at the end of the fourth or fifth instar, whereas othe-- 
individuals had additional instars. Similarly, in the second generation the length of 
larval life to the last molt prior to entrance to period of winter inactivity varied 
because a majority of the larvae entered this period at the end of the fourth instar, 
whereas others developed fifth and sixth instars. 
2 To last molt in second generation ; not including indefinite duration of last instar 
and winter period of inactivity. 
From Table 24 it is seen that during the three-year period the 
average duration of the egg stage each year varied from 7 to 7.16 
days for the first generation and from 6.25 to 7.84 days for the 
second generation. The average duration of the larval period each 
year, for the majority of the individuals under observation, varied 
from 30.1 to 35.12 days for the first generation and from 20.89 to 
32.9 days for the second generation to the last molt. This does not 
include, of course, the indefinite duration of the last instar and its 
winter period of inactivity. Under insectary conditions four instars 
were developed by the majority of the individuals in both genera- 
