cts known as powder-post beetles. Finished hardwood
products such as handles, wagon, carriage and machinery stock,
especially if ash or hickory, are often destroyed by the
powder-post beetles. Construction timbers in buildings, bridges
and trestles, cross-ties, poles, mine props, fence posts, etc.,
are sometimes seriously injured by wood-boring larvae, termites,
black ants, carpenter bees, and powder-post beetles, and
sometimes reduced in value from 10 to 100 per cent. In tropical
countries termites are a very serious pest in this respect.

MARINE WOOD-BORER INJURIES

Vast amounts of timber used for piles in wharves and other
marine structures are constantly being destroyed or seriously
injured by marine borers. Almost invariably they are confined to
salt water, and all the woods commonly used for piling are
subject to their attacks. There are two genera of mollusks,
_Xylotrya_ and _Teredo_, and three of crustaceans, _Limnoria,
Chelura_, and _Sphoeroma_, that do serious damage in many places
along both the Atlantic and Pacific coasts.

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 rat