88 SEVENTEENTH Report StaTtE Entomotocist or MinNEsotA—1918 
to obtain a temperature of 48°C (120°F) and maintain this tempera- 
ture until the heat has penetrated all of the flour or grain which may 
contain insects. In Kansas it is possible to do this during warm sum- 
mer weather, when there is a sufficient amount of radiation, by turn- 
ing on the steam Saturday evening and keeping it on until late Sunday 
night. In this way the mill is cooled down by Monday morning and no 
time is lost. Experiments in Minnesota have shown that it is necessary 
to have increased radiation in order to attain the proper temperature. 
However, this would seem to be a promising field for experiments. 
It has been found that infestations are often spread by the refill- 
ing of flour sacks which have not been thoroly cleaned. In several in- 
stances where storerooms were found to be free from any source of 
infestation the cause of the large number of beetles present in the flour 
was traced directly to the refilling of uncleaned flour sacks. When a 
method of heating the flour sacks in the oven was adopted, the trouble 
ceased. It was found that the empty sacks could be placed in an ordi- 
nary baker’s oven at the usual temperature of 230°C (about 450°F) 
and left for about five minutes, when all of the insects would be killed, 
provided the sacks were not more than three layers deep. As a pre- 
caution against scorching of the sacks they should be placed on pans 
or boards to keep them from coming in contact with the oven. Care 
should also be used not to let the sacks remain in the oven longer than 
five minutes at the temperature indicated above. Boxes and other 
utensils which are used about a bake shop and which may harbor in- 
sects, have also been heated in the oven and all stages of insects killed. 
Large amounts of flour or other stored food products may be 
freed from Tribolium confusum by fumigation or by sifting. Carbon 
disulphide or hydrocyanic acid gas (described above) may be used for 
this purpose. The carbon disulphide is placed in shallow dishes on 
top of the material to be fumigated and the liquid evaporates. The 
fumes, which are heavier than air, settle down into the material and 
kill all insects which may be present. This material is very inflam- 
mable when mixed with air and should never be used near a fire. The 
quantities recommended are about one pound to every 100 cubic feet 
of space. When the material is placed in a tight barrel, about one cup- 
ful of the liquid will be required. The receptacle must be tightly cov- 
ered and left for a day or more, after which the material should be 
well aired. Farmers’ Bulletin 799, United States Department of 
Agriculture, Washington, D. C., contains much information with re- 
gard to the use of carbon disulphide. 
