PROCEEDINGS, 1915. 33 



lager, are well pruned and a heavy drenching spray is given. In the case 

 of the rosy aphis, however, when the stem mother causes the leaf to curl 

 about her like a paper cylinder, the spray must be applied when the aphis 

 first hatches, otherwise it is quite wasted. 



The Woolly Apple Aphis. 



(Eriosoma lanigera, Hausmann.) 



This pest is well known everywhere the apple is grown. The aphid 

 colonies appear as bluish white, cottony patches, which, on closer ex- 

 amination are seen to be made up of a large number of small reddish 

 brown aphids, covered with a white waxy secretion. They are particu- 

 larly abundant upon wounds on the trunk or on a place where a limb 

 has been removed. Later in the season they move out on the smaller 

 twigs and form colonies there. In many countries the woolly aphis at- 

 tacks the roots of the trees and causes its most serious damage in this 

 way, but injury to the roots by this insect in Nova Scotia is rare. 



Life History. Though this insect has been a well known pest for 

 many years, its complete life history has only recently been worked out. 

 The secondary host has been shown to be the elm and the following is a 

 brief summary of the life history of the insect as worked out by Mr. A. C. 

 Baker of the U. S. Bureau of Entomology:* 



The eggs are laid singly in cracks or crevices of the bark, usually on 

 the elm. There hatch in the spring and the first three generations of 

 the insect are prssed on the elm. The leaves of the elm curl and form a 

 characteristic rosette as a result of the work of the insect, and inside this 

 shelter the aphids live. 



Insects of the third generation develop wings and these spring mi- 

 grants fly to apples or related plants, where they settle down upon leaves, 

 stems and water sprouts. The next three generations are on the apple, 

 the last one developing into a fall migrant which flies back to the elm, 

 where the sexual forms are produced. Here mating takes place and the 

 eggs are deposited, one female producing one egg only. As in the case 

 of the other aphids discussed the female sex predominates. 



The foregoing is apparently the normal life history of the insect, but 

 it does not necessarily go through all these stages. In our own work we 

 have found that only a small proportion of the sixth generation become 

 fall migrants, that the insect can be carried on from year to year without 

 any sexual stage intervening and that a number always winter upon the 

 tree in some sheltered place such as cracks or crevices of the bark. It 

 would thus appear that the sexual generation is not an essential stage_in 

 the life of the insect. 



*The Woolly Apple Aphis, Report 101, U. S. Dept. Agr. 



