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



solution of acetic acid. Oak avoocI, the normal host, contains tannin 

 and acetic acid. 



Below is an analj^sis, by the Bureau of Chemistry of this depart- 

 ment, of a section of oak wood from California. 



Table 7. — Analysis of a section of oak icood from California. 



Determination. 



As 1 Moisture- 

 received, free basis. 





Per cent. Per cent. 

 20.36 



Total solids . . . . 



6. 57 8. 25 



Soluble solids 



6.29 7.93 



Insolubles 



0.28 : 0.32 



Non-tans . . . _ 



4.20 ; 5.27 



Tannin 





2.09 1 2.66 



As nearly as could be judged, catechol and pyrogallol tans were present in 

 nearly equal amounts, pyrogallol probably predominating. Pyrogallol was 

 shown definitely by the acetic acid-lead acetate test. The iron-alum test was 

 rather indefinite. Catechol was shown by the bromide test and by the for- 

 maldehyde test. 



THE METAL-PENETRATING ABILITY OF THE INSECTS ASSOCIATED WITH THE 



CABLE BORER. 



During the studj^ of the penetrating power of the cable beetle 

 numerous records were made on the penetrating ability of the asso- 

 ciated insects and a few other species. 



The roundhead Xylotrechus nauticus Mann, was able to penetrate 

 all of the alloys used, the carborundum-coated lead, copper-coated 

 lead, and building paper. (PI. IV, Fig, 4.) It penetrated as many as 

 five thicknesses of lead-antimonj^ alloy and seven sheets of building 

 paper. It made no impression on the sheet zinc or sheet steel. An- 

 other roundhead, Neoclytus conjunctus Lee, penetrated six thick- 

 nesses of the lead-antimony alloy and four of pure lead. It made a 

 slight impression on the sheet zinc, but none on the sheet steel. A 

 third roundhead, Phymatodes nitidus Lee, seemed unable to pene- 

 trate the carborundum-coated lead, but did penetrate one thickness of 

 the lead-antimony alloy and four coats of spar varnish. The fourth 

 roundhead, Callidium yseudotsugae Fisher, made onh' a slight im- 

 pression on the lead. One Xylotrechus larva penetrated five thick- 

 nesses of copper-coated lead and three coats of spar varnish. A bos- 

 trichid larva, Polycaon stoutii Lee, penetrated one thickness of cop- 

 per-coated lead but was stopped hy the carborundum-coated lead. A 

 few powder-post beetles, Lyctus planicollis Lee, penetrated one 

 thickness of lead-antimon}'- alloy and two thicknesses of lead-anti- 

 mony and lead-tin together, but many beetles of this species did not 

 seem able to penetrate any of the alloj^s or the carborundum-coated 

 lead. The predatory clerids were unable to make any impression on 

 the alloys. 



