TWO SPECIES OE MACROSIPHUM. 87 



toes were supplied them in the field they might not seek another 

 host even there. As it is a wholesale migration has taken place 

 each of the seasons these plant lice have been under observa- 

 tion. 



The fact that M. solanifolii colonized readily upon garden 

 peas in the insectary while M. destructor refused the potato 

 (see page ) is not without interest. 



Insectary Host Plant Tests for M. destructor. 



(July- August, 1908.) 



The plants used for these tests were grown from seed and 

 were kept in quarantine for the purposes of this test so that 

 no infestation of the plants by other than the desired aphides 



was possible. 



From Peas to Red Clover. Pisuni sativum L. to Trifolium 



Pratense. 



(a) July 21. A lot of mature specimens and nymphs, re- 

 moved from peas to red clover. July 27. Mature individuals 

 all dead. Nymphs feeding along the clover stems. Aug. 10. 

 One winged form developed. Several living nymphs present 

 in clover. Aug. 12. Aphides all dead. (26-08.) 



(b) Aug. 10. A lot of 15 alate forms which had deserted 

 peas (to migrate) and were present on cloth ceiling of pea- 

 vine cage were transferred to red clover. In less than an hour 

 these had deserted the clover as they had the peas and had 

 gone to the sides and top of cage. No young were produced 

 on the clover. (50-08.) 



(c) Aug. 12. A lot of 10 migrants from peas placed on 

 clover. They deserted the clover at once and did not produce. 

 (50-08.) 



From Peas to Potato Vines {Solanum tuberosum L). 



(d) July 15. A lot of 20 nearly mature apterous indi- 

 viduals transferred from peas to potato plants. July 17. All 

 20 dead. No feeding on the potato took place. They would 

 not remain on the potato but deserted it. (26-08.) 



(e) July 21. A lot of 50 mature apterous individuals 



