June 14, 1924 
Effect of Fumigation 
1113 
The data of Table V on the relative abundance of the rice weevil and the flat 
grain beetle in probes taken at varying points in a wheat bin having warm 
spots indicate, as one might expect, a large number of insects present in the 
warm spots. The data are unsatisfactory in that there are not enough records 
of the abundance of insects in grain having temperatures below 70° F., for at 
temperatures between 70° and 90° F. grain pests are thoroughly active. 
Table V.— Number of Sitophilus oryza and Cryptolestes pusillus found in one- 
ounce samples taken at four depths in bin with varying temperatures ° 
Number of insects in sample from— 
Point 
in bin 
Temper¬ 
ature at 
center 
Bottom of bin 
1 foot from 
bottom of bin 
VA feet from 
bottom of bin 
6 inches from 
top of grain 
Total 
insects 
for 
Sito¬ 
philus 
oryza 
Crypto¬ 
lestes 
pusillus 
Sito¬ 
philus 
oryza 
Crypto¬ 
lestes 
pusillus 
Sito¬ 
philus 
oryza 
Crypto¬ 
lestes 
pusillus 
Sito¬ 
philus 
oryza 
Crypto¬ 
lestes 
pusillus 
probe 
A_ 
°F. 
38 
1 
0 
0 
. 
0 
0 
1 
0 
2 
B. 
38 
0 
1 
3 
0 
1 
3 
0 
0 
8 
C_ 
38 
0 
0 
1 
2 
0 
1 
0 
0 
4 
D_ 
100 
1 
2 
14 
12 
17 
15 
4 
2 
67 
E....... 
90 
0 
18 
1.1 
35 
14 
22 
6 
10 
126 
F__. 
98 
0 
0 
2 
6 
10 
30 
6 
8 
62 
G_.. 
94 
6 
12 
5 
5 
3 
13 
10 
20 
74 
H. 
71 
8 
5 
18 
14 
21 
5 
7 
3 
81 
I. 
93 
3 
4 
8 
13 
16 
27 
6 
2 
79 
J_ 
98 
6 
11 
6 
9 
9 
9 
8 
0 
58 
K . 
98 
0 
4 
4 
5 
17 
16 
9 
0 
55 
« Reading taken where wheat was about 2£ feet deep. 
The data of Table VI are of importance in that they give one an idea of the 
high percentage of wheat kernels actually found infested when examined for 
immature stages beneath the compound microscope. 
The writers can not help but conclude from their observations that the insects 
themselves are capable of developing heat in grain in storage. It does not seem 
probable that there is much truth in the often expressed idea that the heating of 
insect-infested grain is usually due to a fermentation set up by the absorption of 
moisture by the faeces of the insect. The writers have seen seeds (wheat, beans, 
and chick-peas) badly damaged and heating because of insects, that were leathery 
rather than brittle because of the moisture apparently absorbed by the seeds, or 
the faeces in the seeds. Thus badly infested seeds in sack 25 of Table III could 
be pressed flat without breaking because, as the writers thought, of the humid 
conditions produced by the infestation. Yet the fact remains that the heat left 
not only this sack, but all the sacks of chick-peas fumigated with hydrocyanic- 
acid gas in the warehouses, and the wheat fumigated with carbon disulphid in 
farmers’ bins. It may be recalled, also, that Richardson ( 5) and Duhamel du 
Monceau and Tillet ( 1) have said that the heating of seeds ceases often with the 
passing of the infestation (usually after the seeds have been rendered valueless as 
food and filled with excreta). Unless it can be proved that bacteria or other 
organisms causing heat are killed by fumigation with hydrocyanic-acid gas or 
carbon disulphid, there seems no other conclusion than that the activity of cer¬ 
tain stored-product pests is directly responsible for the development of heat 
in grain in certain instances and that fumigation will kill such heat and permit 
the grain to return to normal temperature. 
