2 DAMAGE TO WOOD OF FIRE-KILLED DOUGLAS FIR. 
Another class of wood-boring insects, represented by a number of 
species, attacks the trees three or four years after they die; these bore 
deep into the heartwood, thus causing serious damage. Insects of 
this class will continue to attack the trees year after year as long as 
they find sound wood in which to excavate their burrows. There- 
fore the damage increases year by year until the wood is rendered 
entirely worthless by the borings and by the subsequent decay which 
necessarily follows. 
It is a fact, however, that there is often a great difference in the 
relative damage to individual trees which have died from injuries 
caused by the same fire. Some trees will be ruined in a few years, 
while others will be but slightly damaged and remain sound for 10, 
20, or even, in exceptional cases, 50 years. 
The date or period of the fire or fires is an important factor in rela- 
tion to subsequent injury by insects. It is well known that timber 
killed by fire at some seasons of the year will remain sound much 
longer than that killed at other seasons. 
The character of the primary injury and the date or season of the 
subsequent death of the individual trees is also important. Some of 
the trees will die immediately after the fire, while others will die at 
intervals for a year or more. Those dying at different times and 
seasons will show very different conditions as to subsequent damage 
by wood-boring insects. Then, again, different ages and types of 
trees of the same species will show very different rates of damage, as 
will also different species of trees, 
It is somewhat different in the case of timber killed by bark- 
beetles or defoliating insects, because in such cases the timber usually 
dies within definite periods and is therefore subject to attack by 
special kinds of wood-boring insects. 
REQUISIFES FOR SUCCESS IN PREVENTING LOSSES. 
In regard to methods of preventing losses from damage by wood- 
boring insects to fire-killed timber there are a few fundamental 
requisites for success which should be carefully considered before 
action is taken, Among these are the recognition of the different 
classes of injury and of the importance of expert advice on some 
of the essential details in any plans for extensive operations to pre- 
vent losses. 
CLASSES OF INSECTS AND INJURY. 
Some of the important classes of insects and injury are as follows: 
(1) Certain pinhole borers (ambrosia beetles) attack the sapwood 
as soon as the trees begin to die, but the damage by this class of 
borers is usually limited to the first season. 
