THE CoNFUSED FLouR BEETLE 87 
a time devoted to freeing themselves. Mortality in many cases seemed 
to be due to these mechanical difficulties. 
From the records at hand the percentages of mortality are as fol- 
lows: for the wheat flours, first middlings, 40 per cent; first sizings, 
33 per cent; first low grade, 40 per cent; first tailings, 40 per cent; bran, 
32 per cent; for the other materials, barley flour, 50 per cent; steele- 
cut oats, 32 per cent; rye flour, 55 per cent; white corn flour, 56 per 
cent; rice flour, 12 per cent. These percentages are taken from mea- 
ger data and should not be looked upon as conclusive vital statistics, 
altho they are the result of controlled conditions which approximate 
the optimum. 
METHOpDS OF CONTROL 
The control of Tribolium confusum is the problem of preventing it 
from invading stored food products. In cases where the infestation 
already exists it may be necessary to resort to some method of 
“sterilizing” the infested products. 
So little difference has been found in the susceptibility of the vari- 
ous food products studied in this connection that the number of insects 
which may be found in a given product probably depends very largely 
upon the opportunities which the beetles are afforded to invade the 
product. Flour on the floors of mills and storehouses supports a small 
population of beetles which invade sacks of flour and are then trans- 
ported to other storehouses where the infestation may spread. Among 
the many instances of this which have been found was that of a large 
warehouse which had become badly infested from a single shipment 
of infested rolled rye. The flour which was stored closest to the rolled 
rye contained the heaviest infestation, and that more distant from it 
contained proportionately fewer beetles. 
An infested storeroom or mill may be freed from insects by fumi- 
gation with hydrocyanic acid gas, or it may be heated to the fatal tem- 
perature for insects. Both of these methods have been described by 
Dean in Bulletin 189, Kansas State Agricultural Experiment Station, 
Manhattan, Kansas. 
The fumigation should not be undertaken without detailed direc- 
tions and the temperature conditions must be favorable. Furthermore 
it requires the shutting down of the mill for several days and always in- 
volves a certain amount of risk on the part of the operator. Dean also 
states that the gas does not penetrate the accumulations of flour and 
the cracks, which harbor the insects, so well as the heat does. 
When heat is used to kill the insects in a building it is necessary 
