397 



habitat and spionvmy are discussed under each species. Eriosoma 

 lanigenim (woolly aphis) is not dealt with. The chief object of the paper 

 is to show that the most harmful of all apple aphids in Great Britain 

 is Koch's Aphis pyri, renamed by Schouteden Aphis kochi, and not, as 

 has been stated, Aphis sorbi, Kalt,, which was described from specimens 

 found on Sorbiis aucuparia and is a totally distinct species. The so- 

 called brown, blue and rosy aphis or leaf-curhng aphis of the apple 

 in England should therefore be known as A. kochi. 



Aphis pomi, De G., ranges throughout Britain and Europe generally^ 

 America, South Africa and Tasmania. It often occurs in considerable 

 numbers in Britain, but never in such vast numbers as A. kochi, nor is 

 it so injurious. It mainly lives on the top shoots and beneath the 

 leaves. The whole hfe-cycle seems to be passed on the apple and pear, 

 unUke A. kochi and A. avenae. It can easily be dealt with by spraying 

 whereas A. kochi cannot. 



Aphis kochi Sch., the brown, blue, rosy or leaf-curhng aphis of 



apple, occurs all over Britain and in most parts of Europe, North 



America, Africa and apparently in Australia. All varieties of apples 



and pears serve as food-plants, mostly the former in Britain ; the 



medlar is also attacked. Walker records it from Crataegus oxijacantha, 



Sorbus aucuparia. and Sorbas domesticus, and Passerini on Sorbus 



torminalis, but these records are thought all to refer to the true Aphis 



sorbi. In Britain this species hatches in the latter half of April. It at 



first lives on the tops of the bursting buds and then enters them ; as 



the buds open, it continues to hve on the young leaves, and as these 



individuals mature, the leaf may curl up and partly enclose them. 



They soon produce living young, often with great rapidity, and the 



presence of these, as they grow, further accentuates the curling of 



the leaves. This aphis also feeds on the shoots, giving rise to contorted 



and stunted growth. The first winged forms found by the author 



occurred on 13th June 1899, and they were found onwards until 



29th July, in 1914. Although they become mnged in masses, a few 



winged individuals always occur some time before the main swarm, 



and others later. The winged females are very sluggish, and, like 



those of A. rumicis, collect together in masses, usually choosing the 



underside of a fairly large branch of the tree near its junction with 



the trunk. Many of these groups were noticed in 1915 to die off and 



remain attached" to the branches. This winged summer generation 



migrates in July, its destination being unknown. In the beginning of 



September a few return migrants may appear, but the majority do not 



do so mitil October. These produce the sexual generation of apterous 



oviparous females and alate males. The sexuparae may occur on 



into mid-November, and oviparous females have been found as late as 



the first week in December. The females and males occur under the 



leaves, and when fertilised, the females crawl to the shoots and lay 



their eggs either singly or in small groups, never in dense masses as is 



done by A. p)omi. During the past six years efforts to trace A. kochi 



to other plants have been in vain. No Aphid varies so much in colour 



in the apterous stage. In one district they may all be slaty-grey, in 



another all bluish black, in others most are plum colour or brown, but 



all have a small sprinkhng of pale reddish or pink forms with them ; 



occasionally colonies occur entirely of this colour. Towards the end 



of June a few Coccinelhds, many Syrphids and a few Chrysopid larvae 



