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 live 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. \ if 



Throughout the North it ap- XW^?^^^ 



pears that bluegrass (Poa pra- ^^^^^f 1 ^^^^^^ 



tensis) is the most common host /? jCL. -IIl n^ 



plant of Toxoptera, though it / *r?*'" ** '"Ak \ 



occasionally, on account of favor- /O ?m 



able weather conditions or the //fi /% .Va\ 



scarcity or natural enemies, be- p" f .;. | |' V,|/ \=» 



comes excessively abundant there fit'Y\ 91 JWh 



and escapes to the grains in ll \^S^SSt^// 



destructive numbers. Conse- \\ N^W^r // 



quently it appears that the sexes \\ 7r ^ r u 



normally occur on bluegrass. It « ^ 



IS flko true that thpv will he bpf- FlG - 15 -- The spring grain-aphis: Shrunken and nearly 



is a iso irue mai tney win oe Dei spent oviparous female> Enlarged. (Original.) 

 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 



