566 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
As the common names of this species imply, it feeds on the foliage of 
the rose, and is an introduction from Europe. It is now known to occur 
in the United States and in Canada east of the Rocky Mountains. 
The larvae feed on the upper surface of the leaflets by a characteristic 
chafing method, eating only the soft tissue and leaving the veins and 
undertissues. There is one generation a year (Middleton, 300). 
The larva of Phyllotoma nemorata (Fall.), the birch leaf-mining 
sawfly, is somewhat flattened and whitish, with the head and joints 
of the thoracic legs brownish, and is about two-fifths of an inch in 
length when full grown. There are no black spots in the middle of the 
underside of the thoracic and the first abdominal segments, as In Penusa 
pusilla (p. 567). This sawfly, of European origin, was found in Nova 
Scotia in 1905 and is now known to occur in the Canadian Provinces 
of Nova Scotia, New Brunswick, and Ontario, and in Maine, New 
Hampshire, Vermont, Massachusetts, and New York. It severely at- 
tacks gray, paper, and European white birches, and to a lesser degree, 
red, yellow, blue-leaf, and Alpine birches, and occasionally alder and 
hazelnut. The larvae feed between the upper and lower surfaces of 
the birch leaves, producing large blisterlike or blotch mines which 
remain free of excrement. 
Severely infested trees show a marked reduction in the amount of 
annual growth, and the operators of birch mills have noted that wood 
from severely injured trees does not turn or work up so well as wood 
from uninjured trees. In heavy infestations an increase in the number 
of dead branches and dead tops of trees has been observed, although 
the death of entire trees cannot be attributed directly to this insect. 
Phyllotoma nemorata has one generation annually, and no males 
have ever been found or reared from field-collected larvae and pupae, 
a fact which indicates that the species reproduces parthenogenetically. 
The adults emerge during June and the early part of July, the period 
of maximum emergence varying somewhat with the changes in climate. 
The eggs are deposited singly in slits cut in the tissue of the leaf serra- 
tions, and seldom are more than two or three eggs laid in a leaf. 
Usually there is a characteristic browning of the leaf area immediately 
surrounding the point where the egg was inserted. Hatching takes 
place in 12 to 26 days. The feeding season extends from July to 
October, but the larvae usually become full grown in 47 to 57 days 
after hatching. Usually a larva consumes about 35 to 40 percent of 
the parenchyma in a leaf before completing its growth. Each full- 
grown larva constructs a lens-shaped cocoon or hibernaculum of silk 
within its mine in the leaf (fig. 157). It falls to the ground in its 
hibernaculum and passes the winter there as a prepupal larva. Trans- 
formation to pupal and adult stages takes place in the spring. 
In the United States, birds are the most important predators on 
this insect, and many species have been observed attacking the larvae 
and prepupae, particularly the latter stage after they have dropped to 
the ground in their hibernacula. Several native insect parasites attack 
the eggs, larvae, and prepupae. During the years when the birch 
skeletonizer (Bucculatria canadensisella) is abundant, P. nemorata 
suffers severely from competition. 
Although this sawfly has been recorded in many parts of Europe, 
apparently no outbreaks have ever been reported. Dowden (7/39) 
published on the results of studies conducted in Europe in 1929-34 
by the Bureau of Entomology and Plant Quarantine, and showed the 
