These mollusks, which are popularly known as “shipworms,” are much alike in structure and mode of life.  They attack the exposed surface of the wood and immediately begin to bore.  The tunnels, often as large as a lead pencil, extend usually in a longitudinal direction and follow a very irregular, tangled course.  Hard woods are apparently penetrated as readily as soft woods, though in the same timber the softer parts are preferred.  The food consists of infusoria and is not obtained from the wood substance.  The sole object of boring into the wood is to obtain shelter.

Although shipworms can live in cold water they thrive best and are most destructive in warm water.  The length of time required to destroy an average barked, unprotected pine pile on the Atlantic coast south from Chesapeake Bay and along the entire Pacific coast varies from but one to three years.

Of the crustacean borers, Limnoria, or the “wood louse,” is the only one of great importance, although Sphoeroma is reported destructive in places. Limnoria is about the size of a grain of rice and tunnels into the wood for both food and shelter.  The galleries extend inward radially, side by side, in countless numbers, to the depth of about one-half inch.  The thin wood partitions remaining are destroyed by wave action, so that a fresh surface is exposed to attack.  Both hard and soft woods are damaged, but the rate is faster in the soft woods or softer portions of a wood.

Timbers seriously attacked by marine borers are badly weakened or completely destroyed.  If the original strength of the material is to be preserved it is necessary to protect the wood from the borers.  This is sometimes accomplished by proper injection of creosote oil, and more or less successfully by the use of various kinds of external coatings.[38] No treatment, however, has proved entirely satisfactory.

[Footnote 38:  See Smith, C. Stowell:  Preservation of piling against marine wood borers.  Cir. 128, U.S.  Forest Service, 1908, pp. 15.]

FUNGOUS INJURIES[39]

[Footnote 39:  See Von Schrenck, H.:  The decay of timber and methods of preventing it.  Bul. 14, U.S.  Bu.  Plant Industry, Washington, D.C., 1902.  Also Buls. 32, 114, 214, 266.

Meineoke, E.P.:  Forest tree diseases common in California and Nevada, U.S.  Forest Service, Washington, D.C., 1914.

Hartig, R.:  The diseases of trees.  London and New York, 1894.]

Fungi are responsible for almost all decay of wood.  So far as known, all decay is produced by living organisms, either fungi or bacteria.  Some species attack living trees, sometimes killing them, or making them hollow, or in the case of pecky cypress and incense cedar filling the wood with galleries like those of boring insects.  A much larger variety work only in felled or dead wood, even after it is placed in buildings or manufactured articles.  In any case