54 N. S. ENTOMOLOGICAL SOCIETY. 



On reaching maturity the spring migrants seek their secondary food plants, Plantago 

 lanceolafa and Plantago major, but the former is preferred. We had little difficulty, 

 however, in getting them to reproduce upon major, and in fact most of our insectary ex- 

 periments were carried out with this plant. In the field we have found it on both species, 

 though more numerous on lanceolata. 



In the orchard the winged aphids will be seen clustering on the undersides of the 

 apple leaves before migrating. There was an interval of from one to five days, in our 

 experiments, between the time the migrant reached maturity and deposited its first 

 young on the plantain. This form does not appear to be particularly prolific; the largest 

 number of young produced was only twenty, the smallest five. This may be due to 

 the fact that these insects were reared on the broad-leaved plantain, Plantago mnjor, 

 in place of the narrow leaved variety, Plantago lanceolata , which is their favorite host. 



• SUMMER FORMS. 



On the plantains a varying number of generations are produced, the last being 

 either a fall migrant or a winged male, both of which return to the apple. In our ex- 

 periments during the past season, sixth, seventh, eighth and ninth generation aphids 

 developed into one or the other of these forms and left the plantain. This takes place 

 in a comparatively short space of time, on account of the overlapping of the different 

 generations. 



The summer forms do not reproduce as rapidly as the spring forms, t,h ough one of 

 them has the record for the largest number produced in a single day, viz. twenty-five. 

 The average production per day, however, only amounted, in these experiments, to 1.71. 

 The average length of life after the production of the last young was 5.79 days; but a 

 number lived considerably longer than this, two specimens living twenty-six days, one 

 twenty, two fourteen, two twelve and two ten. The average duration of the produc- 

 tive period was 10.16 days. 



FALL FORMS. 



The fall migrants require twelve to sixteen days to reach maturity, after which they 

 return to the apple where they produce the sexual females. Of those transferred from 

 plantain to apple one began to deposit young the same day, but they usually require 

 from one to five days. From six to twelve young are produced by each fall migrant, 

 the average in our experiments being 8.25. The length of life varied from twenty-two 

 days to thirty days. This season the migrants continued to be produced right up to the 

 time that all the insects were destroyed by freezing weather. 



The males are greatly exceeded by the females in numbers. They are produced on 

 the plantain together with the fall migrants and they fly to the apple about the time that 

 the females begin to reach maturity. There is no definite period, however, as the males 

 were found freshly arriving from the plantain right up to freezing weather. 



The normal length of life of the females was about twenty-five days, but in many 

 cases this is cut short by the arrival of a killing frost. It was found that the females 

 were able to withstand several light frosts, but that a heavy frost killed all those in the 

 trees. Even after this, however, new ones are produced by migrants returning from the 

 plantains, where they have apparently had more protection than the insects on the 

 trees. The eggs are not produced in such abundance as those of pomi. In the insectary 

 the females observed produced only from four to six eggs, but it is quite likely that this is 

 below the normal number. 



