28 BULLETIN 1107, U. S. DEPARTMENT OF AGRICULTURE. 



Nicotine sulphate. — The fumes of this tobacco product acted as did 

 the creosote. Beetles placed in chimney cages with sections of wood 

 treated with it soon died. This effect soon wore off, however, and 

 beetles entered the wood through the insecticide after the sections of 

 wood remained in the open air for a time. When one-third nicotine 

 sulphate was added to black iron enamel and white porcelain enamel 

 the fumes were strong and kept the beetles from entering while the 

 sections were in the small cages. As soon as they had aired for a 

 time the beetles entered. 



Water solution of sod/inn, silicate. — In 1919 a number of sections 

 were treated with this preparation. In only 1 case out of 45 did a 

 beetle enter a treated section, and in this case it appeared to be be- 

 cause of a faulty application. When the material was tested with 

 water, however, it appeared soluble, and therefore its use for cable 

 protection would be impracticable. 



Refined paraffin. — This had no repellent effect upon the beetles 

 while it was cold and hard. Some bored into a cake of it. When 

 the weather was warm it softened enough to kill them when they 

 bored into the wood through it. 



Chlorinated naphthalene compounds. — These were received too 

 late for a thorough test. Several sections of wood were treated and 

 placed in the chimney cages and beetles introduced. The insects en- 

 tered through the thinly coated sections without trouble, but died 

 without entering the thicker coated ones. This may have been due 

 to the fact that it was the last of the season and they were weak. 



Beef tallow. — Numerous sections treated with this were placed in 

 the cages with beetles. During the early part of the season when 

 the weather was warm and the tallow soft the beetles were killed 

 as they attacked. Sections, even after the tallow had melted off, 

 were immune as long as the weather was warm. (PL IX, Fig. 2.) 

 Sections treated later in the season, when the heat did not soften 

 the tallow after it was applied, were attacked by the beetles, which 

 entered the wood and laid their eggs. (PL IX, Fig. 1.) 



Beef tallow -refined paraffin. — Sections treated with a mixture of 

 two-thirds tallow and one-third refined paraffin kept out the beetles 

 as long as the mixture was soft enough to kill them. 



Varnish. — Three and four coats of spar varnish were applied to 

 a number of recently cut sections of oak. The beetles entered these 

 and laid their eggs. 



CABLE EXPERIMENTS. 



Caged cable. — Several thousand beetles were placed in cages con- 

 taining cables suspended in the usual manner by rings from messenger 

 strand. Some of these cables carried the usual current of electricity. 



