THE CONFUSED FLOUR BEETLE? 
(Tribolium confusum Duval) 
By R. N. CHAPMAN 
Introduction 
Perhaps the most widely distributed insect attacking flour and 
other cereals in Minnesota is the confused flour beetle, Tribolium con- 
fusum Duval. During the recent war emergency, when substitutes 
for wheat flour were being used and every effort was being made to 
conserve food, this insect came to the attention of many dealers, bakers, 
and householders. This beetle does not claim the attention of the mill- 
ers as much as the Mediterranean flour moth, which spins silk and 
clogs the machinery, but it is nevertheless a pest which causes them 
much loss. 
While conducting work on the insects affecting wheat flour and 
the so-called wheat flour substitutes, a considerable amount of work 
has been done on Tribolium confusum and this paper contains some 
of the results. This is to be looked upon as a preliminary report on 
work which is still in progress. The fact that the work 1s still in prog- 
ress implies that there is no feeling of finality about the results, but it 
is thought that the material contained in this paper is suggestive of the 
final outcome of the work, and it may be of value to those concerned 
with Tribolium confusum. 
DESCRIPTION OF THE VARIOUS STAGES 
The descriptions of Tribolium confusum in the various stages of 
its life history have been published so many times that it is necessary 
to do little more than call attention to the accompanying plate which 
figures all of the stages (Pl. IV). The figures showing the actual size 
of the eggs as compared with the apparent size, when they are covered 
with flour, deserve attention. When first deposited, these eggs are 
covered with a viscid fluid which causes particles of flour or cereal to 
adhere to them, when it hardens, and in many cases it causes the eggs 
to adhere to the sides or bottoms of sacks or other containers. The 
apparent size of the eggs as they are found in nature depends, therefore, 
upon the coarseness of the cereal in which they are laid. A naked egg 
such as is figured (Pl. IV Fig. 1) measures 0.6 mm. x 0.3 mm., while 
an egg coated with ordinary wheat flour (Fig. 2) measures 0.8 mm. 
x 0.6 mm. and represents about the minimum size for a coated egg. In 
1 Published with the approval of the Director as Paper No. 154 of the Journal 
Series of the Minnesota Agricultural Experiment Station. 
73 
