86 SEVENTEENTH Report STATE ENtomotocist oF Mrnnesota—1918 
each group which do not differ greatly from some of the individuals in 
the wheat flour groups. The group of beetles fed on rice flour show 
the greatest prolongation as a group, while the longest individual life 
cycle is found in the corn flour group. 
Another series of experiments has been carried out at a tempera- 
ture of 26°C in which the total length of the life cycle was recorded 
and no attempt was made to determine the length of the various stages. 
Here, as in the checks for the wheat flours of the first experiment, the 
records of the insects in the different foods are much more uniform. 
The time from the hatching of the eggs until the emergence of the first 
adult was 37 days in the middlings, 39 in the sizings, 38 in the low 
grade, 38 in the tailings, and 39 in the bran. In the other foods it 
was 39 days in the rye flour, 38 in the barley flour, 40 in the corn flour, 
and 47 in the rice flour. The shortest time in the rice flour was thus 
about 20 per cent longer than in the middlings. But all of the larvae 
in the rice flour had pupated by the end of 47 days while one of the 
larvae in the middlings was still feeding at the end of this period. 
The rate of development of the beetles may be influenced by the 
relative fecundity of the beetles in the various foods. The number 
of eggs deposited by females which were restricted to certain foods 
have given the following results: middlings, 32; sizings, 34; low grade, 
41; tailings, 32; bran, 20; barley flour, 50; rye flour, 20; corn flour, 45; 
rice flour, 12. The beetles studied have shown such an amount of 
variation among the different individuals that the limited data at hand 
cannot be considered sufficient for determining the influence of dif- 
ferent foods upon fecundity. Such conclusions must await the com- 
pletion of a series of experiments involving many individuals reared in 
certain foods for many generations. 
The analysis of the factors influencing relative development will 
require a more extensive study, but there are certain facts which are 
brought out by the work thus far. There are individual variations 
which seem to be independent of the food on which the insects are 
feeding. It is possible that the different portions of the kernels which 
constitute the flours are unequally distributed in the mixture as it exists 
in market form and that some individuals, by chance, obtain a ration 
which accelerates growth, while other individuals, by chance, obtain a 
diet which is less favorable for rapid growth. 
The observations show that, in general, the beetles with the pro- 
longed stages encountered mechanical difficulties. They were found 
with particles of flour attached to them and all their efforts for 
