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Journal of Agricultural Research 
Vol. XIV, No. 2 
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being 6o days. This female 
was bom about the middle of 
November (1913) and lived 
until almost the middle of 
the following February 
(1914). The low level in 
reproduction in this series 
was reached during the sum¬ 
mer months. The average 
number of young produced 
during these months is only 
about half that produced in 
early spring or late fall. 
Figure 1 shows further 
that the average number 
of young of the individuals 
during the first year was 
greater than the number 
produced from the indi¬ 
viduals in the second year. 
This would seem to indi¬ 
cate a weakening of the 
strain. If, however, the 
average number of young 
produced during the second 
year in the A series is com¬ 
pared with the average 
number produced in the B 
series during the same 
period it will be noted that 
there were more young in 
the former series than in the 
latter. If the number of 
young aphids during the 
spring of the third year in 
the A series be compared 
with those in the C series 
during the same period it 
will be seen that there were 
more young in the latter 
series than in the former. 
The female representing 
the seventy-first generation 
of first-bom individuals in 
the A series died without 
producing young. 
