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A. sorbi, Kalt. (rosy apple aphis) is dealt with on the basis of 

 extensive rearing experiments carried out in Ithaca in 1914-1916. The 

 synonomy of the species is discussed, the author differing from the 

 view expressed by Baker and Turner that the American species 

 is distinct and should be known as A. malifoliae. [R.A.E., A, v, 49.] 

 He considers the correct synonomy to be as follows : — A. sorbi, Kalt. 

 {A. pyri, Boyer of Koch, not A. pyri, Boyer ; A. malifoliae, Fitch ; 

 A. Jcochii, Schout., of Theobald, not A. kochii, Schout. ; A. pyri, 

 Boyer of Gillette & Taylor). 



The preferred, if not essential, sunmier food-plant of A. sorbi is the 

 thin-leaved plantain, Plantago lanceolata, there being a remarkable 

 parallel between the introduction and spread of this plant and the 

 spread and increasing destructiveness of the Aphid. The life- 

 history and the severe curling of the foliage caused by this species 

 have previously been described [R.A.E. A, iv, 484.]. The repro- 

 ductive capacity of the various generations is shown in a table^ 

 the maximum period for the stem-mother being during the last 

 week in May and the first week in June. A description of aU 

 stages of the insect is given. At Ithaca the migratory forms of 

 A. sorbi may consist of the winged females of the second, third or 

 fourth generation. The author did not succeed in rearing more than 

 four generations on the apple, though in some years there are 

 undoubtedly more. In Nova Scotia the migratory forms have been 

 found to be adults of the third generation- The factors that influence 

 the early or late production of migratory forms have not been 

 sufficiently studied ; the necessity for investigating the influence of 

 climatic factors is urgent, as it has a large bearing upon problems of 

 insect control. 



It has been reported that A. sorbi has been reared throiighout the 

 season upon apple in Ontario, and the offspring of migratory forms on 

 plantain have been transferred to apple and have there produced 

 another generation. The ability of the species to maintain itself 

 on apple alone has not however been confirmed ; if this proves to be 

 the case it may become a pest of the greatest importance. 



The longevity and reproductive capacity of the spring and autumn 

 migrants, as well as the true summer forms on Plantago lanceolata, are 

 illustrated by charts. It is noticeable that the spring migrant has a 

 shorter life and greater reproductive capacity than the spring forms 

 on apple. It has been supposed that as the summer winged forms 

 are produced in such relatively small numbers, they cannot be 

 of great importance in the life-history of the species. The author does 

 not consider a single season's work to be conclusive evidence on this 

 Bubject, and points out that the greater numbers of enemies encountered 

 on plantain necessitates a high productive capacity and also ability 

 to spread to more distant food-plants. 



The autumn migrants begin to return to the apple in Ithaca in late 

 September, the winged females developing first. The males begia 

 to appear somewhat later and continue migrating to the apple well into 

 November. Descriptions are given of these forms. The oviparous 

 females which are the immediate descendants of the autumn migrants 

 infest the smaller twigs and branches, where mating takes place. 

 The eggs, which average about six for each female, are deposited around 

 the base of buds, under small pieces of bark, or in any sheltered position. . 



