82 SEVENTEENTH Report STATE ENtomMotocist oF MrInNesota—1918 
The influence of nutrition in determining the relative invasion of 
the wheat flours has not been measureable as a factor in these experi- 
ments. To determine whether the method would indicate differences 
of nutritive value, coarse sawdust was introduced in place of the bran 
in the wheat flour series and it was found to contain a varying number 
of beetles, principally at the edges where the sawdust and flour be- 
came slightly mixed. It averaged only 6 per cent of the beetles, which 
makes it very evident that the method used does measure the nutritive 
difference between the wheat flours and the sawdust. 
When an experiment has stood for a period of several weeks it 
has been found that the decisive differences between the flaky and fine 
materials tend to disappear. Thus the ratio between the percentages 
of the coarse and fine bran material was 60 per cent and 40 per cent 
examined every 48 hours, but when the experiment was left for a 
period of 26 days it was found that the fine material, contrary to the 
previous findings, contained 53 per cent of the beetles and the coarse 
material contained 47 per cent. An examination of the material after 
it has been exposed to a large number of beetles for an extended length 
of time shows that it has been burrowed by the beetles until it is 
‘“honeycombed” and is apparently more attractive to the insects. The 
beetles may be driven by competition to enter the fine flour and thereby 
alter it and make it a more favorable environment resembling a flaky 
material so far as their tactile responses are concerned. 
In consideration of the relative development of the beetles in the 
various wheat flours and the wheat flour substitutes, an attempt was 
made to determine whether there was a difference in the velocity of de- 
velopment in the various foods, and, 1f so, whether this difference was 
sufficient to account for more insects being found in certain of the foods 
than in others. The experiments were all carried out under controlled 
conditions and all of the experiments of each series were carried on 
simultaneously so that all of the results were directly comparable. 
The first series was started by exposing the material to a number 
of beetles for twenty-four hours and then removing the beetles. Since 
no attempt was made to determine the sex of the beetles used, a defi- 
nite number of eggs could not be expected, but from a dozen or more 
beetles, a few eggs could be depended upon. The vials containing 
the material and eggs were placed in the dark at a known temperature 
and humidity. The material was examined daily except when the task 
of making the records made it impossible for all of the material to be 
studied each day. 
The date of hatching of the eggs is taken from the first daily ex- 
