56 



Biological Studies of Aphis rumicis 



Dwarf French beans. R. 25. 5. 14. Infected with .3 w. v. ??. 10. 6. 14. Some 

 aphids 4th v, gen. present, small size, scattered over plant, some dead; w. v. ? 

 mothers dead. 15. 6. 14. Only five aphids alive, are a. v. ??, very small size, three 

 adult and producing 5th v. gen. 29. 6. 14. Very few aphids present, small size, dark 

 brown colour. 



(6) Mangolds, red beet and sugar beet were infected each with one 

 w. V. ?, 5th V. gen. from Rumex. Three plants of each kind were in- 

 fected, and one a. v. $, 6th v. gen., offspring of the w. v. ? mother, was 

 left to reproduce on each plant. The total number of aphids produced 

 in 14 days was recorded as shown in Table IV. 



Table IV. 



Aphids produced 



14 



14 



14 



Series C. Reproduction of Aphis rumicis on ten varieties 

 OF Broad Beans. 



The experiments of 1914 were continued in 1920, by series C and D. 



As different varieties of broad beans might give a varying degree 

 of susceptibihty, one plant of each of ten such varieties was infected with 

 an a. v. ? (offspring of winged migrant from the winter host) to form 

 the stock plants for infecting others. All the seeds were sown on 

 3. 5. 20. Five plants of each variety were then infected with one a. v. ? 

 (offspring of the apterous mother on the stock plant) from the respective 

 stock plant. The apterous mother on each plant began producing on 

 the 25. 6. 20, and the number of aphids after 14 days was counted, the 

 total numbers being given in Table V. 



The reproduction over 14 days on a further series of broad beans 

 (Sutton's Prohfic Longpod) was tested. The seed was sown on 26. 6. 2. 

 The a. v. ? (taken from stock plant No. 6) on each plant, began to 

 reproduce on 20. 7. 20. The ^-esults obtained are shown in Table VI. 



