J. Davidson 



53 



Three plants of each, kind mentioned above were infected each with 

 one a. v.^ ?, 4th v. gen. from its respective stock plant. After 14 days 

 reproduction, all the aphids produced on each plant were counted. 



Below is shown the progress of the infestation on these stock plants 

 and Table I gives the number of aphids produced. The column " winged 

 forms" in all the tables refers only to adults or advanced nymphs re- 

 cognisable as immature winged forms. 



OS c^ 



f^ Date 



Text-fig. 1. Max. and min. daily temp, of glass house between June 25th and 

 August 4th, 1920. 



Broad beans. A. 22. 5. 14. Infected with 9 w. v. ??. 7. 6. 14. 4th v. gen. are 

 all a. V. ??; large size. 18. 6. 14. Many w. v. $? present; plant heavily infested. 



Horse beans. A. 22. 5. 14. Infected with 3 w. v. ??. 7. 6. 14. 4th v. gen. are 

 aU a. V. $?. 18. 6. 14. Many w. v. $$ present; plant heavily infested. 



Papaver rhoeas. A. 22. 5. 14. Infected with 12 w. v. ??. 9. 6. 14. Reproduction 

 slower than on beans; only a. v. ?? produced. 18. G. 14. Moderate infestation, 

 several w. v. ?$ present. 6. 7. 14. Plants sickly; aphids small size. 



Peas. A. 22. 5. 14. Infected with 3 w. v. $?. 9. 6. 14. 4th v. gen. few in numbers 

 bjit fairly large size, all a. v. $$. 29. G. 14. Aphids moderate numbers, several 

 w. V. ?$ present. 31. 7. 14. Aphids in moderate numbers, many a. v. $?, small size. 



Euonymus europaeus. A. 24. 5. 14. Infected with 4 w. v. $$. 10. 6. 14. 4th 

 v. gen. small numbers but fairly large size, all a. v. ?$. 



^ a. V. = apterous viviparous; w. v. = winged viviparous. 



