520 
Journal of Agricultural Research 
Vol. V, No. 12 
In its attacks on hawthorns the leaf miner tunnels the foliage in the 
same manner as that of the cherry. During the course of our studies it 
has been very evident that the pest is more destructive to certain species 
of Crataegus than it is to the English Morello cherry. As has been rarely 
observed in the case of the latter plant, one may find as many as five 
larvae mining a single leaf. With hawthorns having a relatively small and 
narrow leaf, as C. geneseensis , there may be a;n entire destruction of the 
pulpy tissue, in which event all that remains of the affected leaf is the 
epidermis, which dries up and ultimately falls to the ground. At the 
height of an attack, which occurs when the larvae are reaching maturity, 
hawthorns which are much infested take on a brownish cast and appear 
as if struck by a blight or swept by fire. In decorative plantings the 
destructive work of the insect may assume such a character that the 
attractiveness of certain species of hawthorns as ornamental shrubs is 
seriously marred. 
About Geneva the sawfly leaf miner is most common in the foliage of 
an unidentified hawthorn belonging to the Medioximae group, while 
such species as C. pedicellata and C. punctata , growing in the immediate 
vicinity of the former, have so far shown little or no injury and are gen¬ 
erally exempt from attack. Dr. C. S. Sargent, Director of the Arnold 
Arboretum, writes that the insect has become established in the plant¬ 
ings of Crataegus spp. and that it is especially destructive to hawthorns of 
the crus-galli group and to C* nitida , C. rotundifolia , C. pruinosa , and other 
species. Similar conditions exist at the New York Botanical Garden 
and, as elsewhere, certain species of Crataegus are quite badly infested, 
while a few species have so far been free from attack. 
In the public parks at Rochester, N. Y., notably Genesee Park, the 
insect has in recent years become a serious pest. Hawthorns represent¬ 
ing a wide range of species and grown in extensive numbers feature promi¬ 
nently in certain landscape plantings. In these the sawfly leaf miner 
has become established, and its destructiveness may be readily observed 
during May and June. Some haws have been seriously affected, while 
others have been exempt from injury. Here, again, various hawthorns 
of the crus-galli group have proved to be very susceptible to the pest, 
and certain species of other groups have shown considerable injury. 
DISTRIBUTION OF SAWFLY LEAF MINER- 
As a cherry pest the sawfly leaf miner is definitely known to occur in 
injurious numbers in orchards of English Morello cherry about Geneva 
in western New York and about Germantown, which is located in the 
Hudson Valley. It has been reported to the Station as occurring about 
Schenectady, but the statement of its presence in that locality has not been 
verified. In view of its occurrence in two communities which are widely 
separated, it would seem reasonable to suppose that the pest exists in 
