76 SEVENTEENTH Report STATE ENTOMOLOGIST OF MInNEsoTA—1918 
The feeding activities of the larvae vary with the character of the 
material in which they may be found. In coarse, rolled, or ground 
cereals, the larvae wrap themselves about the pieces of food and hold 
onto them with their legs while they feed. When in finely ground 
material they crawl about, feeding as they go. When the material is 
very fine and the particles inclined to adhere together and form small 
masses, it often causes the larvae much trouble by catching on the hairs 
which project from their bodies and impeding their progress. 
As the time for pupation approaches, the larvae become inactive 
very much as they do just before an ordinary moult, except that the 
period of inactivity is of longer duration and they become more great- 
ly contracted. The pupa lies ventral side up, often with the old larval 
skin attached to the posterior end. It is at first white, later it becomes 
yellowish and at the end of its period it is quite dark brown. 
Foop Hapsits 
Tribolium confusum is known to feed upon a wide range of foods 
and is said to exhibit certain preferences. Dean’ states that while 
it is primarily a flour pest, it also infests corn meal, cracked wheat, 
any dry starchy material, stored peanuts, beans, and even baking 
powder, ginger, and cayenne pepper. He states that it may show a 
preference for the sweet and more oily low-grade flours, but intimates 
that this preference is not a very marked one for the beetles are to be 
found in great numbers in the best patent flours. The general state- 
ment has often been made that insects prefer coarse cereals of a low 
grade. 
In order to determine whether certain preferences actually exist, 
two lines of investigation have been pursued. Stocks of flour and 
ground cereals have been examined in storehouses to determine the 
percentage of infestation in the various products. In the laboratory, 
experimental methods have been employed to study the relative sus- 
ceptibility of the various flours and cereals under controlled condi- 
tions. 
THE RELATIVE INFESTATION OF WHEAT FLOUR AND WHEAT FLOUR 
SUBSTITUTES 
In the examination of the cereals in the storehouses a uniform 
method of sampling has been adopted. A brass tube 2 cm. in diameter 
and 40 cm. in length was sharpened at one end and graduated on the 
1 Bull. 189, Kansas State Agr. Exp. Sta. 1913. 
