128 Food Plants of Aphis riimicis 



28. 6. 13, A few colonies present on the underside of some of the leaves. 



28. 7. 13. Several colonies present beneath the leaves ; nymphs of winged vivi- 

 parous females present ; some of the leaves are crinkled along the 

 veins showing a slight damage due to the aphids ; there are however 

 not very many aphids produced, and the infestation is only moderate. 



Plant No. 24. Onions. 



18. 6. 13. Infected from Euonymus tree growing in Acton Lodge garden with four 



W. V. $'s. 

 28. 6. 13. Aphids all dead. 



Experimetits. Series B. 



In this series of experiments, the writer wished to find out if the 

 winged migrants from Euonymus showed any preference for particular 

 plants, if a choice of food plants were given. 



It was desirable that the aphids should, as far as possible, be under 

 natural conditions. At the same time it was necessary to ensure against 

 infection from other plants, and that the plants should be grown under 

 conditions which enabled constant observations to be made. 



For these reasons, a wooden framework, 33 feet long, 6 feet wide, 

 and 5 feet 6 inches high, was erected over a plot of ground in Acton 

 Lodge garden. This was covered with very fine muslin which was 

 carefully fastened down to the woodwork so that insects could not 

 get in or out. The tent was divided into three compartments by 

 muslin partitions, so that the insects could not pass from one compart- 

 ment to the other. 



Early in April the plot of ground surrounded by the tent was heavily 

 fumigated with carbon di-sulphide. At the end of this month several 

 food plants which had been raised in pots from seed were placed in the 

 tent, and in addition, some seeds of Broad Beans, Shirley Poppies, 

 Mangolds, etc. were sown. 



In Compartment A, the following plants were grown : Broad Beans, 

 Shirley Poppies, Palaver rhoea, Mangolds, Red Beet, Sugar Beet, 

 Swedes, Onions, Rumex sanguineus, Nasturtiums. 



In Compartment B, Broad Beans, Shirley Poppies and Papaver 

 rhoea. 



In Compartment C, Broad Beans and Rmnex sanguineus. 



Each compartment was entered by a door which opened from 

 outside into each compartment separately. 



At the beginning of June (3. 6. 13), Euonymus bushes which had 

 been infected in May with Aphis rumicis from the Euonymus bush B, 



