78 SEVENTEENTH Report STATE ENtToMoLocist oF MINNEsoTA—1918 
outside to read in cc. This tube was thrust in between the stitches at 
the end of the flour sack and could be withdrawn full of flour without 
otherwise disturbing the sack. The sample of flour was then weighed 
and sifted. It was found that when the tube was slowly turned in 
one direction as it was being pushed in, the sample withdrawn would 
be of quite uniform weight. 
Four samples were usually taken from the flour next to the out- 
side of the sack. The sample was sifted with an Excelsior testing set.’ 
The size of the standard bolting cloth varied with the character of the 
material under examination, but No. 5 was used whenever possible. 
After counting and removing the insects, the residue on the bolting 
cloth was taken to the laboratory and incubated to determine whether 
it contained eggs. 
The history of the flour, in so far as it could be obtained, was 
tabulated on the record sheet for use in determining where the prod- 
ucts became infested. All of the establishments recorded on the accom- 
panying table were visited without any advance knowledge of the pres- 
ence of insects. This investigation was undertaken so late in the 
season that insufficient material was examined to give significance to 
the results. However, the results are given here, for they are sug- 
gestive of a line of work which will add to our knowledge of relative 
infestation. (See Records.) 
THE RELATIVE SUSCEPTIBILITY OF WHEAT FLOUR AND WHEAT 
FLourR SUBSTITUTES 
The experimental work on the relative susceptibility of the various 
flours and cereals to Tribolium confusum has proceeded upon the as- 
sumption that other things being equal, susceptibility may influence the 
number of insects which enter a flour in the first place ; or the rate of de- 
velopment of the insects after entrance may lead to their accumulation 
in great numbers. In the first case it might be possible to account for 
the great number of insects in a certain flour by the fact that a great 
number chose to enter it in the first place. In the second case, assum- 
ing that equal numbers of insects entered each of a number of foods, 
the shortening of the life cycle in one of these would, in time, give 
it the appearance of being more susceptible than any of the other 
foods. 
2 The Excelsior testing set, manufactured by Hammond-Humberg Co., Minneapolis, 
Minn., consists of a sifting frame together with the silk bolting cloths No. 0000 
standard to No. 16 standard inclusive. 
