758 RoBeRT MATHESON 
leaves surrounding the cluster are severely curled, distorted, and usually 
blackened by the growth of a sooty fungus in the honeydew. When 
the infestation is very severe, few if any apples may set in such a cluster, 
or, if they do set, they are likely to drop early. 
Not only does the rosy apple aphis attack the flower clusters, but in 
severe infestations it may spread over the entire foliage, tho generally 
most of the injury is low down in the tree around the outer margin. The 
leaves become badly curled, forming tight rolls within which myriads of 
lice are at work and from which migrations to the surrounding foliage 
constantly occur (Plates XIII and XIV). 
This species probably does the severest damage to the fruit of any of 
the three species discussed in this paper. Parrott (1916 and 1917) per- 
formed some interesting experiments on the inhibition of growth of the 
fruit due to the attacks of the three species. He found that the greatest 
inhibition of growth, in both axial and transverse diameters of the fruit, 
was due to the attacks of the rosy aphis. Fruits that have been injured 
are usually elongate, puckered at the calyx end, and somewhat distorted 
(Plates XV-XVII). If not too badly injured, such fruits cling to 
the tree, growing but slightly and giving the so-called “cluster apples’’ 
at picking time. These cluster apples consist usually of from four to 
seven apples on a spur, which are small, distorted, and knotty. In a 
badly infested orchard, cluster apples may form the majority of the fruit 
at picking time. 
THE APPLE-BUD APHIS 
Since the species Aphis avenae hatches from a week to ten days earlier 
than the other two species, it is the first one found on the bursting buds. 
When abundant, as is frequently the case, it may almost completely 
cover the buds. As the buds open, the young lice swarm over the leaves 
but never cause them to curl. Since in this vicinity practically all of 
the descendants of the stem mothers become winged and leave for their 
summer host plants, they do scarcely any serious damage to Base the 
foliage, the fruit, or the developing shoots. 
THE APHIS SITUATION DURING THE LAST OF JUNE EACH YEAR 
Before closing the discussion of injury to the apple, a summary of the 
situation during the latter part of June may be worthy of consideration. 
