8 BULLETIN 170, U. S. DEPARTMENT OE AGRICULTURE. 
damage to pine forests and more often to pine nurseries. They are 
the more capable of injury because there are two generations an- 
nually and they thus have two chances each year to accomplish their 
damaging work. None of these native species can. however, even 
with this advantage, be compared in destructiveness to the European 
species just introduced. This is partly due to the larger size of the 
introduced species and to the greater voracity of the larva, but is 
mainly due to the difference in the attack, which causes a different 
reaction of the tree. 
The larva of the native species of the genus confines itself to a 
single twig and finds its food within this or within a single bud, or at 
most a few buds. This bud or twig dies, but the tree responds with 
the natural growth of the next set of buds and very often recovers 
from the injury without permanent disfigurement. The resulting 
injury to the trees is serious only when these native species are present 
in unusually large numbers. Moreover, each of the native American 
species is more or less confined to a single or a few species of Pinus, 
but the European pine-moth thrives indiscriminately on all species 
of Pinus and has consequently a greater chance to become excessively 
abundant. TVhile several of the native species are continually of 
some economic importance and periodically become a serious menace 
even to larger trees, it is mainly when they occur in large numbers in 
nurseries that they become really troublesome. Large trees become 
checked in their growth by the loss of terminal twigs, but are not 
necessarih T seriously deformed in their future growth, although an 
undesirable forking of the tree top is a quite common result. 
On the other hand, the larva of the European pine-shoot moth is 
very voracious and not only destroys a number of buds and young 
sprouting shoots by eating their interior, but it invariably damages 
the remaining shoots in the cluster by nibbling their bases on the 
inner side. The subsequent growth of these injured shoots, in the 
effort to supplant the destroyed leader, causes greater permanent 
injury to the value of the tree than if they were entirely removed. 
NATURAL ENEMIES. 
Evetria huoliana in Europe is, to some extent, kept in check by a 
large number of parasitic enemies. As early as 1838 Hartig 1 
recorded 14 ichneumonid wasps and 1 tachinid fly 2 which he had 
reared from pupa? of the pine-shoot moth. It has since been ascer- 
tained that there are several other parasites ; among the ichneumonids 
Eatzeburg considered the following three, which he himself had 
reared, as the more important: Pristomerus vulnerator Panz., Cre- 
mastus interruptor Grav., and Orgilus obscurator Hald. 
1 See " Literature," p. 10. - Actio pinipennis Fallen. 
