28 
BULLETIN 1393, U. S. DEPARTMENT OF AGRICULTURE 
LENGTH OF DEVELOPMENTAL PERIOD 
The length of the developmental period of the granary weevil is 
comparatively short during moderately warm weather. The cycle 
from egg to adult is recorded in Table 7. 
Table 
7. — Duration 
of the developmental period of the granary 
weevil 
Number of days in — 
Num- 
ber of 
days 
from 
egg to 
adult 
Moan 
temper- 
ature 
for 
No. 
Number of days in — 
Num- 
ber of 
days 
from 
egg to 
adult 
Mean 
No. 
Egg 
Larval 
Pupal 
Egg 
Larval 
Pupal 
temper- 
ature 
for 
stage 
stage 
stage 
period 
stage 
stage 
stage 
period 
o p 
o F 
] 
g 
20 
5 
30 
80.4 
23 
4 
24 
6 
34 
80.0 
2 
4 
27 
5 
36 
80.4 
24 
5 
32 
6 
43 
77.3 
3 
4 
21 
5 
30 
80.4 
25 
7 
29 
8 
44 
70.4 
4 
4 
25 
5 
34 
80.4 
26... 
7 
51 
10 
68 
64 3 
5 
4 
22 
7 
33 
77.0 
27... 
6 
55 
• 9 
70 
64 3 
6.. 
6 
33 
7 
46 
72.9 
28 
5 
59 
16 
80 
62.9 
7 
6 
30 
6 
42 
73.6 
29 
5 
53 
10 
68 
62.9 
8 
6 
27 
6 
39 
73. 6 
30 
15 
41 
14 
70 
62.9 
9 
6 
26 
6 
38 
73. 6 
31 
10 
40 
10 
60 
63.3 
10 
6 
24 
6 
36 
74.0 
32 
8 
50 
11 
69 
63.1 
11 
5 
24 
6 
35 
71. 7 
33 
9 
42 
15 
66 
65.7 
12 
5 
22 
5 
32 
75.5 
34 
9 
42 
10 
61 
66.0 
13 
6 
24 
5 
34 
75.3 
35 
9 
40 
8 
57 
66.7 
14 
4 
19 
fi 
29 
80.5 
36 
12 
44 
8 
64 
67.0 
15 
4 
34 
7 
45 
81.0 
37 
12 
39 
8 
59 
68.6 
If) 
4 
19 
5 
28 
81.5 
38 
12 
38 
7 
57 
68.6 
17 
4 
27 
7 
38 
81.5 
39 
12 
40 
6 
.58 
69.7 
18 
5 
20 
6 
31 
81.5 
40. 
4 
29 
6 
39 
79.0 
19 
4 
26 
6 
36 
81.5 
41 
4 
25 
5 
34 
79.0 
20 
4 
24 
6 
34 
81.5 
42 
4 
23 
5 
32 
79.0 
21 
4 
23 
5 
32 
81.5 
43 
5 
28 
5 
38 
78.1 
22 
4 
23 
5 
32 
79.3 
44 
5 
30 
7 
42 
70.0 
Several specimens were reared from egg to adult in 28 days, and 
this together with a preoviposition period of about 7 days would 
give a possible complete life cycle from egg to egg of 35 days. This, 
however, is a much shorter life cycle than normal, for in summer the 
average length of the period from egg to adult, as shown in Table 7, 
is between 30 and 40 days, and the preoviposition period may be 
as short as 6 days in midsummer or, when the adult emerges in the 
fall or early winter, as long as 123 or 148 days. In the vicinity of 
Washington, D. C, there are between three and four generations a 
year. 
RESISTANCE TO HIGH TEMPERATURES 
As already recorded by the writers (3), the granary weevil is not 
very resistant to high temperatures. Exposure for a very few hours 
to 115° F., for one hour to 118° to 120° F., or for 30 minutes to 
130° F., will kill all stages. Moderately high temperatures also are 
fatal to the granary weevil if maintained for any length of time. 
Of adults placed in an incubator maintained at 95° F., four-fifths 
died on t he fifth day of exposure, a few survived for 9 days, and one 
for 13 days. Little, if any, feeding occurred during this period and 
no eggs were laid. Eggs incubated at 95° F. failed to hatch, and 
Larvae exposed to this temperature did not complete their develop- 
ment. 
RESISTANCE TO LOW TEMPERATURES 
The granary weevil prefers a cool climate in which to breed and is 
much more resistant to low temperatures than is the rice weevil. 
