28 PROTECTION OF PLANTS, 1915-16 



Like its related species, the grain aphis, this plant louse uses the apple 

 only as one of its host plants. During the winter its eggs ma}' be found, 

 particularly on the fruit spurs and small twigs where they are tucked 

 away in every crack and crevice or under overlapping bud scales. The eggs 

 of the species cannot be separated from those of either the grain or green 

 aphis. They hatch, however, about ten days later than those of the grain 

 aphis and at the same time as those of the green aphis — at Ithaca about 

 April 22 to May 3rd., that is over a period of 10 to 12 days. 



The young of the rosy aphis usually are found hatching as the buds 

 are distinctly showing green. They seem to prefer the opening flower buds 

 and especially congregate on these. The stem mothers grow very rapidly 

 and mature as the apple blossoms are opening. They are then usually 

 congregated, when abundant, on the flower stalks, the leaves surrounding 

 the flowers and even on the flowers themselves. The stem mothers as well 

 as all the succeeding generations of this species are easily recognized. 

 They are larger, almost globular in shape, of a somewhat reddish to purplish 

 color and always covered by a whitish pulverulence. They begin producing 

 young in great numbers and continue producing till the latter part of June. 

 Their reproductive capacity is enormous, varying from 130 to 244 for a 

 single individual over a period of about ?>2> days. 



Many of the young from the stem mothers acquire wings and this serves 

 to spread the second generation quite widely. They usually, however, 

 remain on the lower parts of the trees, though when abundant they may be 

 found on the highest branches. 



The second generation becomes mature and begins producing young 

 the last few days of May and early June. They continue producing young 

 throughout June but their reproductive capacity is not so great as that of 

 the stem mothers, varying from 70 to 162 per individual. A large number 

 of this generation acquire wings and many, no doubt, migrate to their 

 summer food plant though I have not been able to definitely determine 

 this point except under cage conditions. 



The young of the second generation, that is the third generation, 

 reach maturity about the 10th to 15th of June and produce young till nearly 

 the middle of July or in some cases even later. The reproductive capacity 

 of this generation exceeds that of the second, averaging nearly 130 per indi- 

 vidual. All of the descendants of the third generation, that is the fourth, 

 acquire wings and migrate to the summer food plant, the narrow-leaved 

 plantain {Plantago lanceolata). In our work this past season we thus 



