248 
Graph 5 was prepared by plotting the reciprocals of the periods 
against the mean daily temperatures (columns 4 and 5, Table 7). 
No three of the points in this graph appear to lie in a straight line. 
The points at the lower end of the line are too far to the left because in 
computing the mean daily temperatures temperatures below the zero of 
development were included, which prolongs the temperature axis too far 
to the left. Points at the upper end of the line are too far to the right 
because in computing the mean daily temperatures temperatures were 
included which were above the degree of the maximum rate of develop- 
ment and which, therefore, retarded development. The use of the mean 
daily degrees in this part of the graph prolonged the temperature axis 
too far to the right. 
CT 
A 
60 
GrapH 5, Pupal period. Reciprocals of the periods plotted 
against average mean daily temperatures. 
The points from 60 to 68 degrees are lower than they should be 
normally because these represent the portion of the hibernating genera- 
tion which did not pupate until from two to six weeks after pupation 
began in the spring, and were consequently disturbed daily until they 
pupated by having their cocoons torn open to make observations possible. 
The energy expended in repairing their cocoons daily seems to have 
devitalized them somewhat, on account of which a relatively longer 
period was required. Those which pupated last and hence were dis- 
turbed the most had the longest periods relative to the temperature. 
These points should, therefore, be disregarded. 
