52 N. S. ENTOMOLOGICAL SOCIETY. 



May and the first week in June. One or two days after her final moult the insect begins 

 to deposit her young, and according to our experiments the productive period lasts 

 from two to six weeks. The production of young is more rapid at first and gradually be- 

 comes less. From six to nine per day was about the average in our experiments. The 

 maximum number produced in any day was eighteen. The average number of young 

 produced under insectary conditions proved to be 184, leaving out of account those 

 that evidently died from accidental causes. The duration of life after the last young 

 was produced varied from two to ten days. 



SPRING FORMS. 



Normally, in Nova Scotia, there is only one complete generation upon the apple 

 following the stem mother. Under field conditions the great majority of the third gen- 

 eration develop into spring migrants that forsake the apple for the secondary host plant. 

 In the insectary, however, where we kept large numbers of single aphids upon apple 

 seedlings, it was only in rare instances that a winged form appeared. In cases where 

 the young were removed from the mothers at birth and placed on separate plants it was 

 found that with few exceptions we would have a continuous succession of apple-infest- 

 ing generations and, at the approach of winter, the production of sexual forms. 



The females of the second generation reach maturity in from ten to fifteen days 

 and begin to produce young. The average number produced by thirty-seven indivi- 

 duals of this generation was 106.51, but as many as twenty were produced in a single 

 day. The duration of the productive period in this generation is shorter than that of 

 the stem mothers the longest recorded being twenty-nine days and the average much 

 less. 



The average number of young produced by the succeeding apple-infesting forms in 

 the insectary was 36.09. The average age at the birth of the first young for all the apple 

 infesting forms was 13.42 days, the average productive period 15.61 days, the average 

 duration of life after the production of the last young 15.61 days, the average number of 

 young 63.45, and the average length of life 19.70 days. The greatest length of life of any 

 insect studied was sixty days. 



SPRING MIGRANT. 



As previously stated the third generation in Nova Scotia appears to be a definite 

 migrant generation. In the orchard small colonies are occasionally found throughout 

 the summer feeding upon the apple, but the proportion that follow this habit is negli- 

 gible. Only rarely, as far as we have been able to discover up to the present, do mi- 

 grants appear in any other generation than the third. In the insectary,however,where 

 we kept only a single specimen to a plant, we only once secured a third generation mi- 

 grant in all our experiments. Curiously enough, several developed into spring mi- 

 grants in the seventh generation, though this was in the month of September. By 

 crowding a large number of the third generation on a single plant, however, we had no 

 difficulty in securing migrants. Large numbers of the second generation on one plant 

 gave birth to offspring with a large proportion of winged forms, even though the young 

 were placed on separate plants. 



Thus our experiments would seem to indicate that crowding bears a definite relation 

 to the production of migrants in the species, at least under conditions that exist in this 

 province. They would also appear to show that the migrating instinct is not so deep 

 seated in this species as in certain others, notably avenae, which we could not induce to 

 remain on the apple throughout the season. These points will be considered further in 

 our experiments next season. 



