INSECT ENEMIES OF EASTERN FORESTS 567 
importance of many natural control factors. It was found that 
insect parasites killed large numbers of early-instar larvae, before 
they had mined much of the leaf. Five species have been imported into 
the United States, and two of them, Chrysocharis laricinellae Ratz. 
and Phanomeris phyllotomae Mues., have become established. Spray- 
ing with a mixture of nicotine sulfate, soap, and water (p. 53) after 
the eggs have been deposited and before the mines exceed 14, inch in 
diameter will give satis- 
2 > factory control on trees 
— of sufficient value to war- 
rant the expense, partic- 
ularly on ornamentals. 
(See caution, p. 36.) 
Picking the infested 
leaves could be resorted 
to where practicable, and 
especially the gathering 
and destroying of such 
leaves after they fall to 
the ground. 
The birch leaf miner 
(Fenusa pusilla (Lep.) 
(=pumila Klug) ), also 
called the black-marked 
birch leaf miner, is 
whitish, somewhat flat- 
tened, and slightly over 
1% inch long when full 
erown. It has distinct 
black spots in the middle 
of the under side of the 
thoracic and first abdom- 
inal segments. This isa 
European species which 
has become established in 
| North America. It has 
: been reported from Que- 
| bee, Ontario, and the 
e Maritime: Prov inc es, 
Figure 157.—Mines and hibernacula of Phyl- Canada, the New Eng- 
lotoma nemorata in leat of paper birch. land States. and New 
York, New Jersey, and 
Pennsylvania. Gray, paper, and European white birches are its most- 
favored food plants. The young seedling and sprout growth of the 
gray birch is particularly favored. The larvae are leaf miners and 
feed between the upper and lower surfaces of the birch leaves, pro- 
ducing blotches or blisters (fig. 158). The females prefer to lay their 
eggs in newly developing leaves; therefore the tops of trees are most 
seriously affected. 
Fenusa pusilla has three generations and sometimes a partial fourth 
generation during a year in Connecticut. The first adults emerge the 
middle of May, and a generation from egg to adult requires approxi- 
mately 6 weeks during the period of most active development. The 
overwintering generation seems to take about 9 months, of which the 
