PARK AND CEMETERY. 
237 
INSECT DAMAGE TO NATIONAL PARK TREES 
By A. D. Hopkins, Expert in Charge of Forest Insect Investiga- 
tions, Bureau of Entomology, U. S. Department of Agriculture. 
The damage by insects to the living trees 
of the forests and ornamental grounds of 
the national parks consists of injuries to 
the foliage, branches, or the entire tree, 
which mar or destroy their attractive, edu- 
cational and historic features and diminish 
or destroy their commercial value. 
Throughout the forests of the Rocky 
Mountains and the Pacific slope, including 
the national parks, a large percentage of 
the timber has died during the past half 
century. The old standing and fallen dead 
trees, the red foliage of those that died last 
year, and the fading tops of those dying 
now bear evidences of the work of insects 
and are conspicuous examples . of a great 
waste of forest resources. In some locali- 
ties a few scattering trees die each year 
within a township or section; in others, 
clumps of trees, or whole forests, die with- 
in a single year. 
The conifers, which are the predomi- 
nating trees of the western part of the 
country, are subject to a high death rate 
from insect attack. The pines, the spruces, 
the Douglas fir, the balsam firs, the hem- 
lock, the cedars and the Sequoias have one 
or more destructive enemies. 
In the fall, spring and early summer the 
dying and recently dead trees are conspic- 
uous on account of their fading, yellowish- 
red and reddish-brown foliage, as if in- 
jured by fire. When they are in large 
patches or extend over a considerable area 
their death is often attributed by the casual 
observer to forest fires. 
The extent of the damage to the forests 
by insects through the accumulation of 
dead timber and the dying of matured trees 
over large areas is vastly greater than the 
general observer would suppose. In fact, 
the dead and fallen timber is so common 
in ail forests that it has heretofore been 
recognized as a natural and inevitable con- 
dition. Large areas of insect-killed timber 
have been charged to fire without further 
thought or examination to determine the 
real cause. Fallen timber has been attrib- 
uted to storms and scattering dead trees to 
old age. 
During one recent year a reconnoissance 
was made of typical sections in one of the 
national forests, where there was no evi- 
dence that destructive forest fires had oc- 
curred during the past twenty years. It 
was found that the standing and fallen dead 
yellow pine that had died within that pe- 
riod amounted in board feet to nearly half 
as much as that which was then living, 
and of the sugar pine and Douglas fir 
there was one-fourth as much dead as was 
then living, and every dead tree examined 
in the estimate showed evidence that it 
had been killed by insects. 
In the Black Hills National Forest of 
South Dakota over one-half of the timber 
died within about ten years. In Oregon 
and Montana nearly all of the larger pine 
died within a few years on areas of a few 
hundred to 100,000 acres or more. These, 
together with many other examples of ex- 
tensive dying of timber, have been investi- 
gated and found to be caused pimarily by 
insects. These investigations have demon- 
strated beyond question that a vast amount 
of timber is killed by insects every year 
within the forested area of the Rocky 
Mountains and Pacific coast regions. Fur- 
thermore, the accumulation of this dead 
timber and fallen debris is a menace to the 
living, because they furnish fuel for de- 
structive forest fires. The losses from in- 
sect depredations are thus augmented by 
fires. 
The extent of damage to the forest and 
other trees of the national parks has not 
been estimated, and, with the exception of 
investigations conducted in the Yosemite 
and Glacier parks, we do not have much 
direct information as to the damage al- 
ready done. It is plain to us, however, 
that the general conditions are not differ- 
ent from those which prevail throughout 
the regions in which the parks are located 
and in which the destructive species of in- 
sects are known to occur. 
The amount of damage in the parks must 
be considered not only on the basis of the 
commercial value of the forest resources, 
but on that of the aesthetic and educational 
value of the virgin forest of typical exam- 
ples of tree species. The loss of a section 
of the forest which forms the attractive 
feature in a landscape and is the only re- 
maining example of the original type of 
forest growth of that region is far greater 
than that represented by the commercial 
value of the timber, as is also the loss of 
notable veterans and giants of the different 
species. These old forests and old trees 
are at present one of the attractive and in- 
structive features of the timbered areas of 
some of the national parks, and if they are 
protected from their insect and other ene- 
mies they will be even more attractive fea- 
tues in coming centuries. Under present 
conditions these old trees of the virgin for- 
est are in greater danger of being killed by 
insects than are the younger trees. Indeed, 
many of them have been killed within re- 
cent years. 
The three giant sugar- pines on the trail 
from Wawona to Glacier Point and the 
Yosemite Valley are examples. Two of 
them were dead and the other was dying 
when I saw them in June, 1904, and there 
was conclusive evidence that their death 
was caused by the mountain pine beetle. The 
veteran sugar pine known as “Uncle Tom” 
was being attacked at the same time by the 
same species of beetle, and I am informed 
that it died next year. The loss of these 
four giants of the species is irreparable. 
The Sequoias are supposed to be immune 
from depredating insects, but they are not. 
They are more resistant than other species, 
and that is one reason they have lived so 
long. However, each species has a bark- 
beetle enemy which under favorable condi- 
tions is capable of killing the largest and 
finest specimens. I saw one of the large 
redwoods in the vicinity of Eureka, Cal., 
that had been killed by its bark-beetle en- 
emy, and when in the Mariposa Grove in 
1904 I discovered the bark-beetle enemy of 
the big tree in the living bark of a storm- 
broken limb. 
The mere mention of the names of the 
thousands of species of insects, each of 
which causes some peculiar injury during 
the life of the different tree species, would 
occupy more time than is allotted for this 
paper. Therefore we must consider the 
more important of those which are directly 
responsible for the death of the trees. 
The little genus of Dendroctonus beetles, 
or tree-killing beetles, is represented in the 
Rocky Mountain and Pacific slope regions 
by a few species which are more destructive 
to the conifers of western North America 
than all other forest insects combined. 
They are a constant menace to the pine, 
spruce and Douglas fir of the national 
parks. They are certain to be present in 
every park in which there are forests of 
their host trees, and have doubtless caused 
far greater damage than the park officials 
have realized. 
The species, in the order of their de- 
structiveness, are the mountain pine beetle, 
the western pine beetle, the Engelmann 
spruce beetle, the Jeffrey pine beetle, and 
the red turpentine beetle. All but the Jef- 
frey pine beetle of the Sierras are common 
to the northern Rocky Mountains and the 
Pacific slope. Those common to the cen- 
tral and southern Rocky Mountains are 
the Black Hills beetle, the Engelmann 
spruce beetle, the Douglas fir beetle, and 
the red turpentine beetle. There are three 
other species common to the southern 
Rocky Mountains and northern Mexico 
which are of less importance in causing 
the death of trees. 
These insects are small, stout, black to 
reddish-brown beetles, ranging in length 
from about 2 to 9 millimeters, or 0.08 to 
0.32 of an inch. They fly in the period 
from April to October and attack the main 
trunks of the living healthy trees by boring 
into the bark and excavating long wind- 
ing or nearly straight egg galleries between 
the bark and the wood. In this manner 
they completely girdle and thus cause the 
death of their victim. As soon as the bark 
begins to die the eggs deposited by the 
beetles hatch, and the young grubs or larval 
forms complete the destruction of the inner 
bark. All of the broods develop into the 
adult stage within a year and emerge from 
