INSECT DAMAGE TO TELEPHONE AND TELEGRAPH POLES. 5 



INJURY BY OTHER INSECTS. 



It is not to be concluded that injury by the pole borer is the only 

 type of insect damage to poles. Indeed, a very common injur}' is by 

 white ants, or termites. In lines from 10 to 12 years old serious 

 damage by these insects occurred in as high as 15 per cent of the 

 poles, and their work is often present, at least superficiall}', in as 

 high as 75 per cent of the poles under all conditions of site. The 

 damage, however, is usually to the outer layers of the wood, where it 

 is moist or there is incipient decay, and is more superficial and local- 

 ized than that of the pole borer. Nevertheless, the sound heartwood 

 of poles is often completely honeycombed, especially at the base. The 

 work of white ants is found both in sound wood, "doty" wood, and 

 ''sobby " wood. Sometimes a large channel runs up through the core 

 of the heart and the sides are plastered with clay, forming a hollow 

 tube with several longitudinal interior galleries. Their work often 

 extends from 2 to 4 feet above the surface of the ground. They 

 leave the outer shell of the wood intact and work up tlirough the 

 longitudinal weathering checks, covering the exterior of the pole with 

 earth to exclude the light. White ants will damage poles that have 

 been set in the ground only two years. Evidently they enter the 

 pole from below the surface of the ground. 



Injury by a giant round-headed borer is sometimes found in chest- 

 nut poles. The large mines of this borer are found in the sound 

 and decayed wood of poles. Often where there is rot present the 

 heartwood near the surface of the ground is completely honey- 

 combed by this borer. 



Longitudinal weathering checks in chestnut poles are often widened, 

 and other defects enlarged by large, black carpenter ants and other 

 smaller black ants, which thus hasten decay. 



KNOWN EXTENT OF THE DAMAGE. 



The pole borer has seriously damaged as high as 10 to 15 per cent 

 of the chestnut poles which have been set in the ground for from 10 

 to 12 years in lines in North Carolina, Virginia, West Virginia, Mary- 

 land, and the District of Columbia. It has only recently been deter- 

 mined that it has also seriously damaged a considerable proportion 

 of the arborvitse^ telephone poles in part of a line in Illinois. It is 

 evident, then, that this insect is an important factor in decreasing the 

 normal length of service of chestnut and arborvitsp poles. 



POSSIBILITIES OF PREVENTING DAMAGE TO POLES. 



Methods of treating poles superficially by brushing with various 

 preservatives have proved to be temporarily ollicient in keeping 

 out wood-boring insects, if the work is thoroughly done and not 



' Thuja occidentalis. 



