INSECT DAMAGE TO MINE PROPS. 3 



ployed to cover over such parts of their work as would otherwise be 

 exposed to the light, which they carefully avoid. 



It is well known that when once these insects have gained an 

 entrance to the outer moist or decayed layers of wood they can con- 

 tinue their destructive work into the sound heartwood; on this ac- 

 count it is very important to prevent them from becoming established. 



PREATIXTION OF THE IXJI RY TO UNBARKED, ROUND, AND SPLIT PROPS 

 BEFORE PLACEMENT IN THE MINE. 



By simply adapting methods of handling the timbers, before 

 placement, to well-known facts in the life history of the insects a 

 large percentage of injury can l^e prevented. If a sufficient quantity 

 of props be cut far enough ahead of the time when needed, and stored 

 either in the yard at the mine or in a general storage yard most 

 accessible to the largest number of mines, they can be properly 

 handled to prevent insect injury and a reserve supply established. 

 The logs should be barked in the woods within a few days after 

 felling the trees. After cutting into props they should be trans- 

 ported to the place of storage and piled in loose stacks in such a 

 manner as to facilitate rapid drying, guarding against excessive 

 checking. After a reserve supply has been established it will no 

 longer be necessary to cut mine timber during the warmer months 

 when the insects which deposit eggs in the bark or wood are flying. 

 The periods during which these insects are flying vary with the 

 localit}' and the species of insect, but, in general, in the region north 

 of the Gulf States the period of activity is from Aj)ril to the middle 

 ')f October. In all cases where timbers are to be left stacked, either 

 in the woods or yard, the bark must be removed before the end of 

 March to avoid attack by insects. 



B}^ barking and seasoning mine timbers, insect injury before place- 

 ment will not only be prevented, but injury by termites after place- 

 ment will also be delayed or under some conditions even prevented 

 and the length of life of the timbers prolonged. 



Therefore the timber should always be barked except in rare in- 

 stances where it is to be used in workings of a very temporary char- 

 acter. If unbarked round or split props are to be used in temporary 

 workings where it would not be practicable to remove the bark, the 

 trees should be cut during the fall and early winter. As soon as 

 possible after cutting, props should be stacked in " open-crib " piles 

 in a place where they will dry most rapidly, without excessive check- 

 ing, preferably after they have been transported from the woods, be- 

 cause if the inner bark is dried out before the insects begin to fly in 

 the spring the more destructive insects will not attack them. Split 

 props should be piled with the bark side up so that the inner bark 

 will dry. Logs or props should not be left lying on the ground. Un- 



[Cir. 156] 



