4 INSECT INJURIES TO FOREST PRODUCTS. 
Construction timbers in bridges and like structures, railroad ties, 
telephone and telegraph poles, mine props, fence posts, etc., are some- 
times seriously injured by wood-boring larve, termites, black ants, 
carpenter bees, and powder-post beetles, and Beane reduced in 
value from 10 to 100 per cent. 
PREVENTION OF INSECT INJURIES TO FOREST PRODUCTS. 
The problem of artificial control and prevention of insect injuries 
to forest products offers less difficulties perhaps than that relating 
to many other branches of the general subject of forest-insect control. 
In most cases the principle of prevention is the only one to be con- 
sidered, since the damage is done soon after the insects enter the 
wood, and therefore it can not be repaired by destroying the enemy. 
CRUDE PRODUCTS. 
The proper degree of moisture found in the bark and wood of 
newly felled trees, saw logs, telegraph poles, posts, and like material, 
cut in the fall and winter and left on the ground or in close piles 
during a few weeks or months in the spring and summer or during 
the period when the particular species of injurious: insects are flying, 
are some of the conditions most favorable to attack. The period of 
danger varies with the kind of timber and the time of the year it is 
felled. Those felled in late fall and winter will generally remain 
attractive to ambrosia beetles and adults of round and flat headed 
borers during March, April, and May. Those felled during the 
period between April and September may be attacked in a few days 
after they are felled, but the period of danger from a given species 
of insect may not extend over more than a few weeks. Thus certain 
kinds of trees felled during certain seasons are never attacked, while 
if they are felled at other times and seasons the conditions for attack 
may be most favorable when the insects are active, and then the wood 
will be thickly infested and ruined. The presence of bark is abso- 
lutely necessary for eucreetay infestation by most of the wood-boring 
‘grubs, because the egos and young stages must occupy the inner 
and outer portions bated the latter can enter the wood. Some 
ambrosia beetles and timber worms will, however,-attack barked logs, 
especially those in close piles or otherwise shaded or protected from 
rapid drying. A large percentage of the injury to this class of 
products can be prevented, as follows: 
(1) Provide for as little delay as possible between the felling of the 
tree and its manufacture into rough products. This is especially 
necessary with trees felled from April to September in the region 
north of the Gulf States and from March to November in the latter, 
[Cir. 128] 
