July 8, i$>i8 
Toxoptera graminum in the South 
109 
this would have raised the temperature and produced abnormal condi¬ 
tions. At night and during cool, blustery days the curtains were lowered. 
An interior view of the shelter is shown in Plate 12, B. The arrow on 
the left of the figure points to the Toxoptera cages. 
In conducting molting experiments it was found that a smaller type of 
cage than that used for line breeding gave best results. Three-inch 
flowerpots supplied with toy- 
lantern globes covered over with 
cheesecloth proved very satisfac¬ 
tory. Owing to the small size of 
these cages there was less chance 
for the individuals to get lost. 
Black fiber paper, such as is used 
in picture framing, was placed in 
the bottom of the cages, and this 
assisted very greatly in detection 
of the molted skins, which, being 
whitish, were conspicuous against 
the dark background. 
CONCLUSION 
Although valuable information 
on the life history of this species 
in the South has been obtained 
from these studies, further work 
is necessary to prove conclusively 
all the questions raised. One 
point has been proved in these 
investigations, and that is that oviparous forms develop in the latitude 
of Columbia, S. C. Whether or not the strain becomes weaker as it 
grows older requires further experimentation before we may be at all 
certain regarding it. The foregoing experiments would indicate this; 
yet it was found that insufficient control experiments had been con¬ 
ducted with the main series. 
Fig. 8.—Same as figure 7, but in this diagram the aver¬ 
age length of the immature period of Toxoptera grami¬ 
num is plotted against the average temperature for 
that period. 
