THE LEAD-CABLE BORER IX CALIFORNIA. 41 



SUMMARY AND CONCLUSIONS. 



Although the fact is rather astonishing to the layman, insects do 

 considerable damage to various manufactured articles of metal 

 throughout the world. One of the most important of these injuries 

 is that to the lead sheathing of telephone cables in California. This 

 consists of circular holes about 0.1 inch in diameter which penetrate 

 the sheathing. These allow the entrance of moisture, which causes 

 a short circuiting of the wires and the resulting stoppage of service 

 to the public. 



The insect causing this trouble is a " powder-post " beetle belong- 

 ing to the family Bostrichidae. Its technical name is Scolicia 

 deelivis Lee. Normally it lives in the wood of the live oak and other 

 trees as an egg, larva, pupa, and young beetle for about one year. 

 Periodically some beetles attack the cables during the summer sea- 

 son and cause some damage. Practically all of the boring is done 

 near the point of contact of the cable and the rings which suspend 

 the cable from the messenger strand which supports it. This is done 

 because the beetle must have a foothold from which to attack the 

 cable. It obtains the desired foothold by bracing itself against the 

 ring. As moisture is the immediate cause of the trouble, the dam- 

 age usually fails to become apparent until the rainy season com- 

 mences, when there is an accumulation of "troubles" to be located 

 and repaired within a short time. 



The experiments conducted to date indicate that the beetle is able 

 to penetrate any lead alloy used as a cable sheathing or any poison 

 or repellent placed on the sheathing. Probably it is able to penetrate 

 the poisons because it does not feed as it bores through. Theoreti- 

 cally, if any grease or grease compound which will soften in the sun 

 when the beetle is most active is placed on the rings it will stick to 

 the beetle and suffocate it when it tries to bore into the cable. Beef 

 tallow appears to be the best grease for this purpose. Layers of 

 friction tape impede the boring and thin sheets of copper, zinc, and 

 steel prevent it. Sleeves of these metals can be placed around the 

 cable at the rings, but the cost probably would be too great for gen- 

 eral use. At the present time tallowing the rings is the most prom- 

 ising method of control. During the season of 1921 it was found 

 that the beetles were unable to penetrate pure gum rubber. 



Xo definitei results Avere obtained from experiments with the vari- 

 ous types of suspension rings. The beetles in the cages would not 

 enter at any of them. It is believed that the new type of ring, made 

 of flattened steel-wire stock, galvanized, which the telephone com- 

 panies are now installing, is better from the standpoint of prevent- 

 ing attack by the beetle than the older one. 



