REPORT OF THE SOCIETY 29 



found four full generations to develop on the apple. In the fall return 

 migrants appear and deposit egg-laying females on the apple and so the 

 annual cycle is completed. 



The work of this species on the apple is very characteristic and should 

 easily be distinguished from that of Aphis pomi. As previously pointed out 

 they congregate around the flower buds, around the developing fruits and 

 on the under side of the foliage. Rarely are they found present on the 

 succulent shoots, and when they are present are found on the underside of 

 the leaves, curling them. This species causes practically all the severe 

 curling of the foliage. A single rosy aphis on the under side of a leaf will 

 frequently cause the leaf to become tightly curled and only a few are required 

 to cause all the leaves on a fruit spur to become severely curled and dis- 

 torted. Later they congregate in immense numbers on the developing 

 fruits, particularly about the calyx and stem ends, causing them to become 

 elongate, gnarled, and distorted. Frequently such work results in all 

 the apples of a single cluster remaining on the tree, never fully developing 

 and giving us what the fruit growers designate as "cluster apples." Some- 

 times these "cluster apples" may drop off in June, but many remain till 

 picking time. When this louse becomes abundant, as it frequently does in 

 June, owing to its enormous reproductive capacity, every leaf and fruit 

 cluster on the trees may be infested and the result is the entire loss of the 

 crop and the weakening of the trees. This is especially true if the ordinary 

 natural energies of plant lice fail to appear at the proper time, due as it seems 

 to me, to cold or inclement weather conditions which do not seem to affect 

 the rosy aphis. 



The Green Apple Aphis 



(Aphis pomi De G.) 



The green apple aphis or apple leaf aphis is generally considered a 

 recent introduction from Europe (1897). In my work I have shown that 

 this species has been present in American orchards ever since the middle 

 of the nineteenth century. This species remains on the apple throughout 

 the season and has no alternate food plant. It is quite restricted in its 

 tastes, being found on apple, pear, mountain ash, and quince. It is only 

 on apple, however, that it does serious injury. Like the two species already 

 discussed, it has been sadly confused in all our entomological literature. 

 Not until 1897 was it definitely identified and Smith (1900) published 



