J. Davidson o9 



Poppies. E. (Shirley.) 19. 6. 20. Infected as above. 29. 6. 20. Aphids going 

 poorly, small size, plants poor. 5. 7. 20. Aphids now going well, many immature 

 winged forms. 



Peas. E. (Carter's Laxtonian Dwarf Pea.) 19.6.20. Infected as above. 25.6.20. 

 A small colony going; killed off the apterous mothers. 30. 6. 20. Twenty aphids 

 present; small size; three a. v. ??, remainder w. v. ?$ (not adult). 14. 7. 20. Both 

 the a. V. 9? and w. v. ?? have produced young. 29. 7. 20. Aphids along mid ribs 

 of leaves, developing slowly, small size. 2. 8. 20. Killed off the aphids, .5 a. v. $?, 

 many immature w. v. ??. 



Dwarf French beans. E. (Carter's Canadian Wonder.) 19. G. 20. Infected as 

 above. 2. 7. 20. Twenty aphids present, scattered over the plant, small size, several 

 dead, one a. v. $ adult. 5. 7. 20. Three a. v. $? adult, very small size, producing 

 young. 26. 7. 20. Aphids increasing in numbers, very small size, all a. v. ??. 28. 7. 20. 

 Plant in flower, aphids on flower heads and young seed pods, slightly larger size. 

 2. 8. 20. KiUed off the aphids; small size; all apterous forms. 



Enonymns. E. 16. 6. 20. Infected as above. 29. 6. 20. Moderate number of 

 aphids produced, a. v. ?? and w. v. ??. 20. 7. 20. Many w. v. ??. 



General Discussion. 



{a) Influence of Food Plants on Rejirodnction. 



It will be seen from the foregoing data that, given a favourable food 

 plant, and favourable conditions of temperature and humidity, rapid 

 reproduction will result. A comparatively high reproduction figure with 

 rapid development was maintained on broad beans, while on peas, 

 mangolds, sugar beet, red beet and poppies, the figures were con- 

 siderably lower and the progress of the infestation was somewhat slower. 



On dwarf French beans in 1914 the aphids fared very badly, only 

 a few young were produced and the colony eventually died out. Again 

 in 1920 on the variety Carter's Canadian Wonder, the aphids progressed 

 very slowly and poorly, many died and those which remained ahve 

 developed into small, dwarf individuals, producing only a few young. 

 However, it was possible to keep them going on the plant from 19. 6. 20 

 to 2. 8. 20, at which date the plant was flowering, some of the aphids 

 on the young developing pods making a httle more progress. The 

 experiment was stopped on 2. 8. 20. 



Similarly on peas in 1914 the reproduction figure w^as low and the 

 development period retarded, although, after two months, a number of 

 aphids were found. 



In the 1920 experiments, on dwarf peas (Carter's Laxtonian Pea 

 and Carter's Little Marvel), a few aphids of small size were produced 

 and the development period was prolonged. 



