INSECT ENEMIES OF EASTERN FORESTS 495 
directed spines. Just prior to emergence of the moths the pupae are 
protruded from the cocoons. 
The moth of the birch skeletonizer (Bucculatriz canadensisella 
Chamb.) has a wing expanse of about ~; inch. The forewings are 
brown, marked transversely with diagonal white bars, and the 
hind wings are gray. The body is brown and white. The eggs are 
white, disk-shaped, and are deposited singly and scattered over the 
leaf. The full-grown larva is 
about 14 inch in length and 
yellowish green. Small, flat, 
white, molting webs are very 
noticeable on the leaves where 
larvae are present (fig. 118). 
The small brown — spindle- 
shaped pupa is enclosed in a 
brownish-white cocoon. This 
cocoon is ribbed longitudinally 
and is fastened to the under side 
of a leaf or to debris on the 
ground. The insect is generally 
distributed in Canada and the 
northeastern part of the United 
States, west to Minnesota and 
southward in the higher alti- 
tudes to North Carolina. The 
larvae show a preference for 
gray, paper, yellow, and Euro- 
pean white birches. Black  Fuicure 118.—lull-grown larva and molt- 
birch is also sometimes infested. ing web of the birch skeletonizer (Buc- 
Tl th t b tec culatrix canadensisella), X 4... (Cour- 
1e pest has not been recorde (ecg Coun AGE TDE SE) 
as feeding on red birch. 
The adults are active from the last of June to the last of July. The 
larvae hatch from the eggs in about 2 weeks, each boring through 
the bottom of the egg directly into the leaf, where it makes a serpen- 
tine mine. It feeds as a mmer for 3 or 4 weeks and then comes out 
and spins a small, flat, white web within which it molts. After molt- 
ing, the larva emerges from the web and feeds externally on the soft 
parenchyma of the leaf, skeletonizing it. In about 4 days it molts 
again in the same manner and completes its feeding in another week, 
when it drops to the ground and spins its cocoon. Thus the total larval 
period requires from 6 to 7 weeks. Freshly spun cocoons may be 
found from the last of August to late in September. The species 
hibernates as pupae in the cocoons. There is one generation each year. 
When this insect is abundant, the mining of the leaves by the young 
larvae and the skeletonizing by the older larvae may cause complete 
defoliation. Outbreaks occur at frequent intervals, and the birches 
over wide areas are severely attacked. This defoliation occurs toward 
the end of the growing season, and undoubtedly affects the growth 
the following year. For control, spray with a stomach poison (p. 53). 
The full-grown larva of Bucculatrix pomifoliella Clem., the apple 
bucculatrix, or ribbed cocoon maker of apple, is about 14 inch long, 
with a brown head and a dark yellowish-green body. ‘The larvae 
feed on apple and hawthorn and are sometimes abundant on un- 
792440°—49___39 
