134 Food Plants of Aphis rumicis 



4. 7. 13. Urtica sp. . . . . A small species of nettle, about a foot high, is infected. 



The colonies are forming along the apex of the 

 stem and along the mid-rib of the leaves, causing 

 the terminal leaves to cluster together ; nymphs 

 of winged females are present. 



4. 7. 13. Dahlias . . . . One Dahlia plant has two or three large colonies of 



big apterous females on it. The aphids are col- 

 lected along the flower-stalks, towards the base 

 of the flowers. 



18. 8. 13. Nasturtiums . . . . These plants are growing beneath the Dahlias. The 



aphids have now left the latter plants, and there 

 are several colonies present on the Nasturtiums. 



— 9. 13. Chenopodium sp. . . A few of these plants are still infested with aphids. 



— 9. 13. Urtica sp. . . . . A few aphids still present on these plants. 



General Conclusions. 



The general results obtained in these experiments have already been 

 indicated in the notes given about the various plants. 



It is seen that, in the experiments, series A, as the different genera- 

 tions of winged migrants were produced they were transferred to 

 different host plants. It was thought the previous plant host upon 

 which the aphids were produced might have an influence on the degree 

 of infestation of the succeeding host plants to which the winged migrants 

 were transferred. The results obtained do not, however, give sufficient 

 evidence of this. It will be necessary to carry out this experiment 

 with a large number of plants, the number of aphids produced on the 

 different plants in a specified period of time being counted. Further, 

 it will be necessary to find the variation in the number of aphids produced 

 on different plants of the same species, for the purpose of comparison, 

 before definite conclusions can be drawn. 



The Euonymus bush A (series A) became heavily infested with 

 Aphis eiionymi in February by the rapid reproduction of the original 

 small colony. The bush had been put into the greenhouse and the 

 sheltered conditions no doubt favoured this rapid reproduction. 



The Euonymus bush B which was infected with winged viviparous 

 females from A did not become heavily infested until several weeks 

 had elapsed, although by the middle of May it was almost smothered 

 with the aphids. 



The third set of Euonymus bushes which were infected from Euony- 

 mus B early in May had only a few small colonies on them by the 

 beginning of June. On the third of this month they were placed in 

 the muslin tent and although winged forms were produced towards 



