t)AViDSON — biological Studies of ApMs rumicis L. 807 



Euonymus E3. — 18. 8. 20. Infected with a. v. ? 2 and winged forms from 

 Euonymus Ej. 24. 8. 20. A. v. ? ? producing young ; only one winged form 

 producing, remainder Will not settle on the plant. 31. 8. 20. Only a few Aphids 

 on the plant, small size, apterous. 14. 10. 20. The plant is shedding its leaVes; 

 a good number of aphids present ; small size ; many winged forms ; $ $ and 

 sexual ? ? present. 



Fu ndatr'i X 

 1!^ V. gen. 

 Zl"^ Vgen. 



Fig. 1. 



Table illustrating appearance of winged and apterous forms of Apliis rumicis on Rumex. 



1st V. gen., etc., = 1st viviparous generation ; • = a. v. ? ¥ ; O = w.v. ? ¥ . 



(d) Successive Viviparous Generations reared on Bumex. 



Eumex plants were grown in pots and infected with a. v. ? 5 and w. v. ? ? 

 respectively, in the different generations. 



The first infection was to Patmex No. 1 with one Fundatrix of Aphis 

 rumicis from Euonyinus europaeus on 13. 4. 14. 



The last infections were Paimex Nos. 16 and 17 with w. v. S ? and a. v. ? ? 

 respectively, of the 7th v. gen. from Eumex No. 14 on 16. 7. 14. 



The aphids made rapid progress, and were usually of large size and dull 

 olive green colour. 



In some generations only apterous forms were produced, although winged 

 forms always appeared in later generations, when the aphids were left to re- 

 produce on the plant. 



The appearance of the winged and apterous forms is shown in fig. 1. 



