. Insects injurious to forests and forest products. of the pole with the ground, necessitating the frequentresetting or even the replacement of the damaged poles. Theseirregular galleries of the grub (Plate II, fig. 1) run both horizontallyand longitudinally throughout the heartwood, and are sometimes 7inches long, but vary with the individuals, which show great chfFer-ences in size. The borers usually work in the outer layers of thewood at the base of the pole for a distance of from 2 to 3 feet below,and sometimes from 1 to 2 feet above the line of contact of the polewith the surface of the g
. Insects injurious to forests and forest products. of the pole with the ground, necessitating the frequentresetting or even the replacement of the damaged poles. Theseirregular galleries of the grub (Plate II, fig. 1) run both horizontallyand longitudinally throughout the heartwood, and are sometimes 7inches long, but vary with the individuals, which show great chfFer-ences in size. The borers usually work in the outer layers of thewood at the base of the pole for a distance of from 2 to 3 feet below,and sometimes from 1 to 2 feet above the line of contact of the polewith the surface of the ground. The greatest damage is to that areajust below and just above the surf ace of the ground (Plate I, fig. 3);here the conditions of air and moisture are most favorable. Oftenthe entire butt up to a distance of from 4 to 6 feet and higher,according to the depth of setting, is mined. The numerous galleries,often very close together, completely honeycomb the wood in a zone Bui. 94, Part I, Bureau of Entoniolofy, U. S. Dept. of Agriculti Plate Fig. 1. Fig. 2. Work of the Chestnut Telephone-pole Borer. Fig. 1.—Gallery of the chestnut telephone-pole borer, showing pupal chamber with the en-trance plugged with excelsior-like wood fibers; work near base of pole, below 2.—Mines of the chestnut telephone-pole borer near surface of ground. Natural size.(Original.) DAMAGE TO CHESTNUT POLES HY INSKCT^ 3 to 4 inches in from the exterior of llic poles; tliis so weakens lliepoles that they break oil eh)se to (he sin lace of the j^ronnd. Thebasal 2 feet is usnally sonnd. Kven if the (huna»i:e is not seriousenono^h to cause the poles to break oil under strain, they are likely togo down during any storm, and thus j)ut the wire service out of com-mission; such damaged poles are a serious menace along the right ofway of railroads. The beetle will attack poles that are perfectlysound, but evidently prefers to work where the wood shows signs ofincipient decay; it will not wo
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectelectri, bookyear1910
