238 
the bark to fly in search of new victims. 
Each species has its peculiar habits in the 
choice of host trees, method of attack and 
period of development. 
The mountain pine beetle attacks the 
mountain or silver pine, sugar pine, west- 
ern yellow pine, lodgepole pine, and evi- 
dently all other pines of the northern 
Rocky mountains and the Pacific slope. 
The adult beetles fly in the period from 
July to October, inclusive. When abun- 
dant they concentrate their attack on 
clumps and patches of trees. Their long, 
nearly straight egg galleries and radiating 
larval mines soon kill the bark on the main 
trunks, but the foliage of the infested trees 
remains green and apparently healthy until 
the following May and June. It then be- 
gins to change to a pale green and later 
to yellowish and brown. By the time all 
of the foliage is dead, about the 1st of July, 
the overwintered broods of beetles begin 
to emerge. By the middle of August most 
of them are out of the dead trees and have 
entered the living ones. 
This is by far the most destructive in- 
sect enemy of the pine within its range, 
and under present conditions is a constant 
menace to the forests of matured or mer- 
chantable sized timber. It can be con- 
trolled by felling the infested trees and by 
removing the infested bark from the main 
trunks without burning the bark or tops. 
This work must be done during the period 
between the 1st of October and the 1st of 
July to destroy the broods of the beetle 
before they emerge. Whenever the timber 
can be utilized the product will pay all ex- 
penses. If it has no commercial value it 
will cost on an average 50 cents a tree 
for the required treatment. After an out- 
break is under control the living timber 
can be easily protected from further dep- 
redations by giving prompt attention to the 
felling and barking of any clumps of dying 
trees found during May and June. Rangers 
or fire patrolmen can be instructed so that 
they can do this and anything else that is 
required to maintain control. 
The western pine beetle attacks the west- 
ern yellow pine, the sugar pine and the 
Jeffrey pine. The beetles fly in late June 
to October, inclusive, and usually attack 
scattering individual trees, often selecting 
the larger and older examples. The adults 
excavate winding egg galleries between the 
inner living bark and the wood and the 
larvae transform to the adult stage in the 
outer bark. The beetles begin to fly and 
attack the trees in June and continue the 
attack until October or November. The 
first generation develops and emerges in 
August to November, and the second gen- 
eration passes the winter in the trees that 
are killed by it in the summer and fall. 
The foliage of the infested trees begins 
to fade and turn yellow in a few weeks 
after the trees are attacked by this beetle. 
The summer broods of the first generation 
leave the trees by the time the foliage is 
reddish brown, but the overwintered broods 
PARK AND CEMETERY . 
do not emerge until the following May and 
June, in some cases several months after 
the foliage is brown. 
This species is next in importance to the 
mountain pine beetle as a destructive en- 
emy of the pine, and the two species often 
combine in their attack. In this combined 
attack the western pine beetle is a second- 
ary enemy of the trees because it follows 
the attack of the other species. When it is 
the primary enemy it is responsible for the 
death of a few scattering trees each year 
throughout the forest which results in the 
accumulation of dead timber. In the ag- 
gregate, this accumulative loss is very ex- 
tensive, involving as it does the largest and 
best trees. 
It can be controlled and the living tim- 
ber protected from its ravages by felling 
the infested trees during the period be- 
tween the 1st of October and the 1st of 
June and removing the bark from the main 
trunks and burning it. It is necessary to 
burn the bark, because the broods of this 
species transform in the outer bark. They 
are not destroyed by simply exposing the 
inner bark, as is the case with the moun- 
tain pine beetle. 
The characteristic habits of the Jeffrey 
pine beetle are similar to those of the 
mountain pine beetle and therefore it re- 
quires the same treatment. 
The Douglas fir beetle attacks the Doug- 
las fir, the big-cone spruce and the western 
larch. The beetles fly in April and May 
and enter the living bark on healthy trees 
and on trees that have been injured by fire 
and those that have been recently felled. 
In habits of attack and general character- 
istics the Douglas fir beetle is similar to 
the mountain pine beetle, except that the 
former begins to fly earlier in the season 
and the foliage of the infested trees begins 
to die in the fall. It is very destructive to 
the Douglas fir throughout the Rocky 
Mountain region from British Columbia to 
Mexico, but is much less so on the Pacific 
slope and especially toward the coast. It 
can be controlled by felling the infested 
trees during the period between the 1st of 
September and the first to middle of the 
following April and removing the infested 
bark from the trunks without burning 
Tire red turpentine beetle is the largest 
species of the genus Dendroctonus. It be- 
gins to fly in April and is active until Oc- 
tober and November. It attacks the pine 
and rarely the spruce, but as a rule con- 
fines its operation to the base or basal por- 
tion of the trunks. While its normal habit 
is to breed in the bark of stumps and logs 
of newly felled trees, it often infests the 
bark on healthy trees. Tt rarely kills a 
tree, but is the cause of a large percentage 
of the basal wounds known as “cat faces” 
and fire wounds, so commonly met with in 
the pine. This is a far more difficult spe- 
cies to control than the others because it 
breeds in the stumps of felled trees and 
the base of those killed by the other spe- 
cies or by fire. Valuable individual trees can 
be protected by cutting the beetles out of 
the bark as soon as their presence is indi- 
cated by masses of exuding resin mixed 
with reddish boring dust. 
Wherever there is continued lumbering 
operations, the red turpentine beetle con- 
fines its attack to the stumps, but in the 
national parks and private grounds, where 
a limited amount of timber is cut, or where 
the ravages of the mountain pine and 
western pine beetles have been controlled, 
it is likely to cause more or less extensive 
damage to the living timber for a year or 
two after. 
In combating the other beetles in the na- 
tional parks care should be taken to remove 
the bark from the stumps whenever they 
are found to be infested with this pest. 
The Engelmann spruce beetle attacks the 
Engelmann spruce, blue spruce, and any 
other species of spruce found within its 
range, but does not attack the pine, Doug- 
las fir or balsam fir. It flies in the period 
from June to August and attacks the bark 
of the main trunks of the older or ma- 
tured trees. Its habits are similar to those 
of the mountain pine beetle, except that it 
flies earlier in the spring. When the trees 
begin to die the needles fade to a pale 
green and fall before they change to yellow 
or brown, but the bare twigs present a 
grayish brown appearance. The infested 
trees are easily located in the fall and early 
spring by the fallen needles and the bare 
twigs of the tops. 
This species occurs from British Colum- 
bia to Mexico, and at times is very de- 
structive to the Engelmann spruce forests. 
It can be controlled by felling the infested 
trees and removing the bark from the main 
trunks during the period beginning with 
the 1st of October and ending by the mid- 
dle to last of May. 
The Black Hills beetle is by far the most 
destructive insect enemy of the pine of the 
central and southern Rocky Mountains and 
the Black Hills of South Dakota. Its hab- 
its are similar to those of the mountain 
pine beetle, and the same methods are 
adopted for its control. 
There are certain conditions in the ad- 
ministered as well as in the natural forests 
which contribute to the multiplication and 
destructive work of these Dendroctonus 
beetles. One of the most favorable condi- 
tions is an extensive forest of matured and 
old trees of pine or spruce, because in the 
beginning of an invasion such trees are 
more often the first to be attacked and 
killed. Trees in such a forest injured by 
lightning or storms often form centers of 
infestation, in which the beetles increase to 
sufficient numbers to enable them to kill a 
few trees, and then the invasion is started, 
year after year increasing in force until a 
large percentage or all of the timber is 
killed. They then attack the young trees, 
and often waste their energies on saplings, 
in which the broods fail to develop. 
It is a common belief that severe 
droughts weaken the trees and thus con- 
