92 SEVENTEENTH Report STATE ENtToMoLocist oF MinNEsoTA—1918 
SUMMARY 
1. The larval life of Tribolium confusum is composed of six 
instars which may be distinguished by the measurement of the head at 
its widest point. 
2. A method of examining flour or cereal to determine the 
amount of infestation, has been adopted which makes it possible to 
express the results in terms of the beetles in a given weight of flour. 
For this purpose the sample of flour is taken from the sack by means 
of a brass tube which may be thrust in between the stitches at the end 
of the sack. The sample of flour withdrawn is then weighed and 
sifted through a bolting cloth and the residue retained by the bolting 
cloth is incubated to determine whether any eggs are present. The 
number of insects present may be expressed by a computation of the 
number per kilogram of material. 
3. A study of the relative susceptibility of various wheat flours 
and wheat flour substitutes by means of a jar with removable partitions, 
has made it possible to determine the number of insects attracted to 
each of a number of flours used in the experiment. The results of 
this method make it seem that coarse flaky material is slightly more 
attractive than fine or granular material. However, by crawling 
through a fine flour the beetles cause it to become honeycombed and 
thereafter the beetles enter it as readily as they do the coarse flaky 
material. 
4. A comparison of the rates of development of beetles in various 
foods, under uniform conditions, has shown that the life cycle may be 
slightly longer in some foods than in others and that this difference in 
the rate of development is confined very largely to the last larval 
instar. 
5. The differences in the relative infestation which workers have 
noticed in mills are not accounted for by the experimental methods 
employed in this work but it is suggested that these differences may 
be due to the methods of handling various products which give the 
beetles a better opportunity to enter some of them than others. 
6. Materials which have passed through a No. 3 bolting cloth will 
contain no eggs. To exclude the larvae of the first instar a No. 9 bolt- 
ing cloth must be used. 
7. The heating of flour sacks before they are refilled has been 
found to control the beetles, when accompanied by a general practice of 
cleanliness about storerooms. 
