The More Important Apple Insects. 79 
require 2 years to complete their transformation. from the egg to the adult 
stage, this difference being attributed to climatic and food conditions and the 
time of hatching. 
Fortunately this borer works close to the bark surface, making it a compara- 
tively easy matter to remove the larve with a knife without inflicting much 
injury to the tree. After the roughened bark has been scraped and the borers 
removed, it is advisable to paint the surfaces with either a coal-tar creosote 
or pure white-lead paint. If these surfaces are repainted from time to time, 
new infestations will be largely prevented. While this insect is not always 
readily detected, its location is usually indicated by a small drop of moisture 
and the dark pasty-like frass 
which is exuded from the feed- 
ing area. 
WOOLLY APPLE APHIS.” 
The woolly aphis is unlike 
the other aphids found on the 
apple in that it attacks the tree 
both above and below ground. 
The aerial colonies when 
abundant are quite conspicuous 
(fig. 167). They are found 
upon the trunk, limbs, and 
twigs, being concentrated on 
tender growth or wherever the 
wood has been injured, as by 
tree-crickets, the periodical 
cicada, ete. The aphid colonies 
appear as whitish, cottony 
misses, beneath which are the 
reddish insects themselves. 
The twigs often become more 
or less deformed as a result of 
the attack. On the roots the 
aphids cause swellings and de- 
formities (fig. 168) which often involve most of the roots of the tree, resulting in 
a sickly or stunted tree of but little fruiting capacity. It has been recently deter- 
mined that the woolly apple aphis is native to America. Its present occurrence is 
wide, it being found in practically all of the apple-growing districts of the world. 
It is particularly serious in the semiarid regions of the West, where the dry 
climatie conditions apparently favor its development. The principal food plants 
are the apple and elm, and those of lesser importance include thorn apple, 
quince, pear, and mountain asb. 
The life history of this insect is rather intricate. Briefly, winter eggs are 
laid in crevices of the bark on the elm and occasionally on the apple. The 
eggs deposited on the former are brownish and are covered with delicate, waxy 
hairs, and they hatch in the spring with the opening of the elm leaf buds, upon 
which the young aphids feed. As soon as winged aphids are produced on the 
elm some migrate to the apple, where they establish colonies which feed thereon 
during the summer. In addition to wintering in the egg stage, some wingless 
individuals remain above and below ground on the apple in certain districts 
where the winters are not too severe. Some of the root forms remain under- 
Ic. 167.—Aerial colonies of the woolly apple 
aphis. 
*% Hriosoma lanigerum Wausmann. 
