47 2 
Journal of Agricultural Research 
Vol. I, No. 6 
CHARACTER OF TREES ATTACKED 
The trees attacked are apparently healthy, and infested ones can not 
be detected by their outward appearance. The only way in which to 
detect the larva is to remove the bark and expose the cambium, where 
at a glance you can generally recognize the new galleries from the old 
ones, since new larval mines are only faintly darker than the living 
cambium; in fact, they are sometimes of a delicate pink color, whereas 
all the old work is generally dark brown. In Vilas and Oneida Counties, 
Wis., the trees in the vicinity of Tomahawk and Trout Lakes were care¬ 
fully examined by Mr. S. A. Rohwer last fall (1913), and no evidence of 
the cambium miner was found in white birch (Betula populifolia), red 
oak (| Quercus rubra), red maple (Acer rubrum), or sugar maple (Acer 
saccharum). 
Pith-ray flecks were found in red oak (< Quercus rubra) at Charter Oak, 
Pa., by Mr. T. E. Snyder and in mountain holly (Ilex monticola) at 
Endeavor, Pa., by Mr. F. C. Craighead, but the particular insect or 
insects causing them are not yet known. 
LIFE HISTORY OF THE SPECIES 
METHODS OF REARING 
Numerous experiments were conducted while rearing this species. All 
the breeding jars were placed in a pasteboard box, which was put in an 
ordinary soap box lined and covered with about five thicknesses of news¬ 
paper. This box was kept outside during the winter in an inclosed shed. 
The frost penetrated all the protective coverings, but not so thoroughly 
as though the boxes had been completely exposed. Jars containing 
earth and sand gave the best results in these rearing experiments. From 
April 15 to May 12, 1913, six adults emerged. On May 1 a single adult 
which was reared from the larva emerged, a hymenopterous parasite 
emerging from another pupa case on May 13. 
THE EGG 
The writer unfortunately did not succeed in securing the egg of this 
species, but it is apparently deposited in the fork of two branches which 
are about 5 to 8 years old and near the top of the tree. From the shape 
of the ovipositor (PI. LXI, fig. 4) the egg is more than likely deposited on 
the outside of the bark, as the mine, which has been traced from a twig to 
the base of the tree, a distance of 40 feet, starts from this point like a hair 
line and, increasing in width as it goes down the trunk, reaches a width 
of one-eighth of an inch at the base. 
THE larva 1 
The larva (PI. LXI, fig. 1) is white, opaque, and cylindrical, averaging 
from 20 to 25 mm. in length and 1 mm. in diameter. One larva, collected 
1 The larva of this species was discovered by Mr. H. P. Brown and was first shown to the writer by Mr. 
T. E. Snyder. 
