80 SOME INSECTS INJURIOUS TO FORESTS. 



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 pe- 

 riod 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 cer- 

 tain 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 Avhen the insects are active, and then 

 the wood will be thickly infested and ruined. The presence of bark 

 is absolutely necessary for successful infestation by most of the wood- 

 boring grubs, because the eggs and young stages must occupy the in- 

 ner and outer portions before 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, 

 while the late fall and winter cuttings should all be worked up by 

 March or April. 



(2) Do not leave the round timbers in the woods or on the skid- 

 ways during the danger period, or, if this is unavoidable, take every 

 precaution to facilitate the rapid drying of the inner bark by keeping 

 the logs off the ground, in the sun, or in loose piles, or else, if possible, 

 the opposite extreme should be adopted and the logs kept in water. 



(3) Remove the bark within a few days after the trees are felled, 

 from poles, posts, and other material which will not be injured by 

 checking or season cracks. 



(4) Take advantage of the proper months or seasons in which to 

 fell or girdle different kinds of trees to avoid danger. 



Damage to products cut from saplings and left with the bark on 

 can be prevented by transporting the material from the woods soon 

 after it is cut, so that it will not be left in piles or bundles in or near 

 the forest during the season of insect activity. Damage may also be 

 prevented by care not to leave the material stored in one place for 

 several months. 



Pinhole damage to stave and shingle bolts cut during a warm 

 season can be prevented by removing the bark from the timber as 



