02 
Of the five individuals involved in Table XI the two last hatched 
from the egg March 24, the other three on March 27. This table 
indicates the influence of high temperatures on reproduction, but 
also shows that these affect the individual female to varying degrees. 
The totals for the life of individual females show that all of these 
were in the vigor of life, not having reached the decline at the time 
the observations were made. 
These tabulations are taken from records of regular rearing and 
reproduction investigations, and were selected wherever there 
occurred a number of consecutive days with temperatures varying 
both above and below freezing during each 24 hours. 
By referring to the continuous rearing by the junior author it 
will be observed that with favorable conditions a female Toxoptera 
will produce young every day during the most vigorous portion of 
her life, the exceptions being toward the close thereof. 
It would probably be well to mention in this connection some 
observations of the junior author in regard to the amount of cold 
that can be endured by Toxoptera. 
On November 13, 1908, several viviparous females that had been 
producing young were frozen solidly in a block of ice. They were 
thawed out after 8 and 24 hours, respectively, and all died. These 
may have been somewhat weakened by age, however, so on the 14th 
2 oviparous females, 1 winged viviparous female, 1 adult viviparous, 
and 2 individuals that had cast the third molt were frozen in a block 
of ice and allowed to remain so for 24 hours. About an hour after 
being thawed out, at a temperature of about 45° F., 1 oviparous 
female and the winged female turned dark and died, the others keep- 
ing color, but showing little signs of life. About 3 hours after 
there were signs of life among the remaining ones; 7 hours after 
thawing out they were still feeble; 24 hours after thawing out the 
temperature was raised to 60° F and 1 molted. On the third clay 
after being thawed out there were 2 young in the cage. Six days 
later all were dead except the one that was giving birth to }^oung, 
and her progeny. This will give some idea of the tenacious grip 
Toxoptera has on life. 
Attention may properly be called to the fact that unless the utmost 
caution is employed in the examination of plants for newly-born 
young there is great likelihood that some of them may be overlooked. 
Thus they may be born one day under a high temperature but remain 
undiscovered until later, when the temperature is much lower, and of 
course be credited to the later date. In the light of all of the observa- 
tions made by those engaged in these investigations, the minimum 
temperature under which reproduction begins is about 40° F. Pos- 
sibly reproduction may occur under some obscure favorable circum- 
