THE SPRING GRAIN-APHIS OR GREEN BUG. 
51 
REARING METHODS. 
All of the rearing work, unless otherwise stated in the text, was 
conducted out of doors under as nearly normal conditions as it was 
possible for us to secure. The wheat plants on which the Toxop- 
tera were confined were grown in flowerpots and covered with 
lantern globes, over the top of which was drawn a very thin fabric 
commercially known as swiss. The 
pots were placed on a rearing stand 
having one side hinged in such a 
manner that it could be let down in 
fair weather and closed up in case of 
gales or severe beating storms. This 
stand with its contents is illustrated 
in Plate II, figure 1 . A thermograph 
was placed in this stand, and thus 
continuous records of temperature 
were secured. 
In the middle of the summer of 
1907 two series of investigations were 
begun and were continued until De- 
cember to determine the number of 
generations. In both 1908 and 1909 
series of generation studies were begun 
in spring with the egg (fig. 11) and 
continued until the egg-laying forms 
appeared in the fall. In making these 
observations, the first individuals to 
hatch from the eggs in the spring 
were isolated; the first-born from 
these were in turn isolated, and this 
process was continued throughout the 
season until the egg-laying forms ap- 
peared. The last-born was also kept 
and the same mode of procedure con- 
tinued until fall, as was the case in the line of the first-born. All 
young other than the first-born of the first series and the last-born 
of the second series were counted each day and destroyed. In this 
manner, each series being considered, we would arrive at the maxi- 
mum and minimum number of generations. During these three years 
a vast amount of data, besides that on the number of generations, 
was thus accumulated. (See table, pp. 52-57.) 
Fig. 11.— The spring grain-aphis: Eggs as 
deposited on leaf: a, Dorsal view; 6, lat- 
eral view. Greatly enlarged. (Original.) 
