INSECT INJURIES TO FOREST PRODUCTS. 393 



Tropics to this country in the form of round logs, with or without the 

 bark on, are commonly damaged, more or less seriously, by ambrosia 

 beetles and timber worms. It would appear, from the writer's investi- 

 gations of logs as received at the mills in this country, that the prin- 

 cipal damage is done during a limited period from the time the trees 

 are felled until they are placed in the fresh or salt water for trans- 

 portation *to the shipping points. If, however, the logs are loaded on 

 the vessel direct from the shore, or if not left in the water long enough 

 to kill the insects, the latter will continue their destructive work during 

 transportation to this country and after they arrive until cold weather 

 ensues or the logs are converted into lumber. It .was also found that 

 a thorough soaking in sea water, while it usually killed the insects at 

 the time, did not prevent subsequent attack by both foreign and native 

 ambrosia beetles; also, that the removal of the bark from such logs 

 previous to their immersion did not render them entirely immune. 

 Indeed, it was found that those with the bark off were attacked more 

 than those with it on, owing, doubtless, to the greater amount of 

 saline moisture absorbed and retained by the bark. 



From the foregoing it will be seen that some requisites for pre- 

 venting insect injuries to round timber are: 



(1) To 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 cutting should all be worked up by 

 March or April. 



(2) If the round timber must be left in the woods or on the skid- 

 ways during the danger period, every precaution should be taken to 

 facilitate rapid drying of the inner bark, by keeping the logs off the 

 ground, in the sun, or in loose piles; or else the opposite extreme 

 should be adopted, and the logs kept in water. 



(3) The immediate removal of all of the bark from poles, posts, and 

 other material which will not be seriously damaged by checking or 

 season cracks. 



(4) To determine and utilize the proper months or seasons to girdle 

 : or fell different kinds of trees. Bald cypress in the swamps of the 



South are girdled in order that they may die and in a few weeks or 

 months dry out and become light enough to float. This method has 

 been extensively adopted in sections where it is the only practicable one 

 by which the timber can be transported to the sawmills. It is found, 

 however, that some of these girdled trees are especially attractive to 

 several species of ambrosia beetles (figs. 43, 44, and 45), round-headed 

 borers (tig. 46), and timber worms (fig. 47), which cause serious injury 

 to the sapwood or heartwood, while other trees girdled at a different 



