38 INSECTS INJURIOUS TO FOREST AND SHADE TREES. 
of an inch in length; the thorax is brown, has a short obtuse horn ex- 
tending obliquely upwards from in front, and there is a white line on 
the back extending from the top of the horn to the hinder extremity. 
( Harris.) 
26. THE OAK BLIGHT. 
Eriosoma querci Fitch. 
Order HEMIPTERA ; family APHID. 
A species of blight, or a wooly aphis upon oak limbs, puncturing them and exhaust- 
ing them of their sap. 
This blight is very like a similar insect upon the basswood. The 
winged individuals are black throughout, and slightly dusted over with 
an ash-gray powder resembling mold. The fore wings are clear and 
glassy, with their stigma-spot dusky and feebly transparent, their rib- 
vein black, and their third oblique vein abortive nearly or quite to the 
fork. It is 0.16 long to the tips of its wings. (Fitch.) 
27. THE WHITE OAK SCALE-INSECT. 
Lecanium quercifex Fitch. 
Order HeMiIprEeRA ; family Coccip 2. 
Adhering to the smooth bark of the limbs of the white oak, in June, an oval, 
convex, brownish-black scale, about 0.30 inch long and 0.18 wide, its margin paler 
and dull yellowish. (Fitch.) 
28. THE QUERCITRON SCALE-INSECT. 
Lecanium quereitronis Fitch. 
Order Hemiprera ; family Coccipz. 
On the small limbs of the black oak, a scale like the preceding but smaller, and ot 
a nearly hemispherical form ; its color varying from brownish-black to dull reddish and 
pale dull yellow, with a more or less distinct stripe of paler yellow along the middle 
of its back, and the paler individuals usually mottled with black spots or stripes. 
Length, 0.20; width, 0.16 inch. (Fitch.) 
These scales are parasitized by Platygaster lecanii Fitch. 
29. 'THE OAK-TUMOR GALL-FLY. 
Cynips quercus-tuber Fitch. 
Order HYMENOPTERA ; family CYyNIPID”. 
On or near the ends of the small limbs and twigs of the white oak, hard irregular 
swellings thrice as thick as the twig below them, the bark upon them of a brighter 
cherry-red color than elsewhere, and their substance internally corky and woody ; 
produced by the stings of a small black gall-fly with dull pale yellow antennx, mouth 
and legs, its hind shanks and its antennwe towards their tips being dusky, its length 
0.08 and to the tips of its wings 0.13. (Fitch.) 
30. THE OAK-TREE GALL-FLY. 
Cynips quercus-arbos Fitch. 
Order HYMENOPTERA ; family CYNIPID2. 
Swellings similar to those above described, growing on the tips of the limbs of aged 
and large white-oak trees; producing a small black gall-fly having all its legs and 
