PERIOD OF OVIPOSITION. 
79 
not reach maturity at all in case of an early winter. After reaching 
maturity they will, when accompanied by the male, begin ovipositing 
in from 3 to 9 days; if the weather is warm, in from 3 to 4 days. 
The period, then, from birth to oviposition varies from about 14 to 
44 or 45 days. Females will, in rare instances only, oviposit without 
first having been with the male. They will five unfertilized from 31 
to 71 days without ovipositing, the abdomen becoming very much 
distended, and, upon dissection, 6 or more fully developed eggs may 
be found. In one case a female deposited 2 eggs without having 
been with a male, but no development occurred within the egg and 
it shriveled and dried up within a few days. When nearly through 
ovipositing the female becomes shrunken and misshapen, as shown 
in figure 15. (Compare with fig. 9.) 
PLACE OF OVIPOSITION. 
Throughout the North it ap- 
pears that bluegrass (Poa pra- 
tensis) is the most common host 
plant of Toxoptera, though it 
occasionally, on account of favor- 
able weather conditions or the 
scarcity of natural enemies, be- 
comes excessively abundant there 
and escapes to the grains in 
destructive numbers. Conse- 
quently it appears that the sexes 
normally occur on bluegrass. It 
is also true that they will be bet- 
ter protected from the extremes 
of temperature among tall, rank growing bluegrass than they would 
be on the grains in open, bleak fields. 
In only a very few instances have we been able to find the sexes 
upon the growing grains in the fields. It is an easy matter, how- 
ever, to locate them upon bluegrass in waste places. They appar- 
ently prefer dead or dying leaves and crawl out near the tip of the 
leaf, where it has begun to fold, and here deposit their eggs. (See 
fig. 11.) Several old females have been found at the same time 
within the curl of a leaf, and as many as 14 eggs have been found 
upon a single leaf. 
PERIOD OF OVIPOSITION. 
Here again, as in the case of viviparous development, varying 
temperatures are probably the main factor in determining the length 
of the productive period. Eggs continue to develop within the 
bodies of the females, apparently, as the embryos do within the 
Fig. 15.— The spring grain-aphis: Shrunken and nearly 
spent oviparous female. Enlarged. (Original.) 
