4 BULLETIN 887, U. S. DEPARTMENT OF AGRICULTURE. 
THE EGG. 
The egg (PL I, A) is light glossy brown, oval, and flattened. One 
end is slightly truncate and one side distinctly concave, the depressed 
area being elongate and covering half the central surface of the side. 
Length 0.6 mm., width 0.3 mm. t 
THE LARVA. 
The larva (PI. I, B, G; PL II, B, D) is creamy white with a brown 
head, the average length of full-grown specimens being about 15 mm. 
and the width slightly more than 2 mm. The thoracic and ab- 
dominal segments from the first to the tenth are uniform in width. 
Segments 11, 12, and 13 taper abruptly to a blunt point. Through- 
out, the body is very sparsely clothed with short, stiff hairs. 
The larvae feed almost exclusively on the inner bark, although 
occasionally, where the bark is thin, they will gnaw slightly into the 
sapwood. When feeding in the excrescences of black knot or stem i 
tumor they penetrate into all parts of the porous tissue; also, after 
feeding at the edge of dead areas on the tree, full-grown borers some- 
times penetrate into near-by decaying wood to construct their 
cocoons. Usually, however, feeding is confined to the bark of the 
trunk and larger branches. 
The completed burrows vary greatly in shape, but are usually in 
the form of broad, elongate, central spaces with short galleries leading 
off in different directions. 
Larval activity begins early in the spring and is marked by the 
ejection of fresh, reddish castings through the bark and, often, by a 
few drops of brownish water oozing from the wounds. Active 
feeding has been observed in West Virginia as early as the last of 
March. The larva winters in a silk-lined hibernaculum constructed 
in that part of the burrow where the larva chances to be when over- 
taken by the cool weather of autumn. (PL- I, G.) Some of the 
larvae attain full growth in the fall, and, after wintering in their 
hibernacula, construct cocoons in the spring without further feeding. 
These cocoons are formed by reshaping and adding to the hibernacula. 
In West Virginia there are both one-year and two-year larval 
periods, the duration of this stage of the insect's existence evidently 
depending somewhat upon food conditions but more upon the time 
in the season when the larva hatched. Apparently, larvae from 
early-laid eggs usually transform to adults the following season, 
having thus a one-year life cycle, while those from late-laid eggs 
live in the tree as larvae over two winters, having a two-year life 
cycle. On account of the difficulty of obtaining eggs, no individuals 
were reared under constant observation from eggs to adults. Over a 
hundred newly hatched larvae, however, were collected at various 
times in the summer and planted in apple trees where their develop- 
