Tue ConFrusep FLour BEETLE 83 
amination at which larvae were observed. Thereafter the larvae were 
measured at each examination and the measurement of the head, at the 
point of its greatest width, and the total length of the larva were re- 
corded. 
The graphs (Plates II and III) are arranged in columns, with the 
records of the individual beetles placed one above the other in each col- 
umn. The graphs of the beetles in the various foods are grouped 
together. The time in days represented by the vertical divisions of 
the chart, each large division representing ten days; and the stages of 
the life cycle of the beetles are represented by the horizontal divisions 
of the chart. The daily temperature is recorded at the top of each 
column of graphs. 
The first day of the egg stage is represented by an open square, 
because the exact time of oviposition is not known within twenty-four 
hours. Thereafter the definite records are represented by solid black 
squares. Upon the appearance of the larva the record moves up one 
space to record the beginning of the next stage of the life cycle. At 
the time of each moult, as evidenced by the increase in the head meas- 
urement, the record moves up one space. At the end of the record the 
appearance of the adult is recorded with an “X.” If the record of the 
emergence of the adult is not known within twenty-four hours, the 
“X” is placed in an open square. 
When open squares are used in the records, they are placed hypo- 
thetically from a study of the complete records of other individuals. 
At the top of the record for each of the wheat flour groups, the record 
of the checks is shown. These beetles were subjected to the same 
conditions as the others except that they were not interrupted for the 
taking of measurements. Consequently the check records are straight 
lines and show only the duration of the entire life cycles. 
It will be noticed that the records are very similar for the first 
twenty-two days and that the variations in the length of the stages 
come in the latter part of the larval life, particularly during the last 
instar. While there is considerable variation among the larvae feed- 
ing on the different wheat flours, it is to be noted that all of the checks 
are of the same length. The variations must, therefore, be attributed 
to other factors than the nutritive value of the food. The fall of tem- 
perature toward the end of the experiment will, of course, account for 
the prolongation of stages then incomplete, but would not account for 
the total difference between the long and short stages. . 
The records of the beetles fed on the wheat flour substitutes show 
the greatest variation, yet, even here, there are some individuals in 
