314 Journal of Agricultural Research voi. xviii, no. 6 



By April 4, the earliest date at which insects hatched and lived to be- 

 come adults, the buds had commenced to swell, and many of them showed 

 a little green. Within two or three days the majority of them had begun 

 to open, providing an abundance of food for the young stem mothers. 

 These could be found clustered on the terminal buds, which open earliest, 

 frequently well down between the very small leaves. 



By the time the stem mothers had become adults many of the buds 

 were entirely open and their leaves had completely expanded. The 

 stem mothers almost invariably located themselves upon the petioles of 

 such leaves, head downward. The young migrated, almost immediately 

 after birth, to the under surface of the leaf, where a cluster of them was 

 soon formed. 



SPRING FORMS 

 PERCENTAGE OP ALATE FORMS 



During the season of 19 15, four generations of this species (after the stem 

 mother) were bred on apple. Migrants appeared in all generations. Of loi 

 aphids reared to maturity in the second generation 89.1 per cent were 

 alate. In the third generation, of 34 insects 58.4 per cent were alate.^ 

 In the fourth generation 98.5 per cent were alate, only i insect out of 67 

 being apterous. All young from this single apterous aphid of the fourth 

 generation bore wings, and during the season of 19 14 all insects of the 

 fourth generation were winged. This seems to be the normal condition. 



SPRING APTEROUS FORM ON APPLE 

 LENGTH OP NYMPHAL LIFE 



The average duration of the nymphal period of the spring apterous 

 form was eight days, varying from seven to nine. Three insects born on 

 April 20 became adults in seven days. The mean temperature for the 

 period was 66.3° F. Three other insects, born on April 28, required 

 nine days to reach maturity with a mean temperature of 61.4°. Both 

 lots of insects averaged about six days for the first three months. The 

 mean temperatures for this period were 65° for the early brood and 62° 

 for the later. Moreover, this difference in mean temperature was due 

 almost wholly to the temperatures obtaining on the sixth or last day, 

 when temperature has the least effect on the stages in question. 



REPRODUCTION 



Complete records of reproduction for the spring apterous form were 

 obtained with only six individuals. The average reproduction of these 

 six was 73.5 young. The greatest number of progeny from one mother 

 was 88, while the smallest number was 51. The average duration of the 



> The reason for the high percentage of wingless insects in this generation is that only a few were reared, 

 and of nine young from one mother six became apterous. 



