ng grubs, since the eggs and young stages must occupy
the outer and inner portions before they can enter the wood. Some
ambrosia and timber worms will, however, attack barked logs,
especially those in close piles, and others shaded and protected from
rapid drying.

The sapwood of pine, spruce, fir, cedar, cypress, and the like
softwoods is especially liable to injury by ambrosia beetles, while
the heartwood is sometimes ruined by a class of round-headed borers,
known as "sawyers." Yellow poplar, oak, chestnut, gum, hickory, and
most other hardwoods are as a rule attacked by species of ambrosia
beetles, sawyers, and timber worms, different from those infesting the
pines, there being but very few species which attack both.

Mahogany and other rare and valuable woods imported from the tropics
to this country in the form of round logs, with or without bark on,
are commonly damaged more or less seriously by ambrosia beetles and
timber worms.

It would appear from the writer's investigations of logs received at
the mills in this country, that the principal damage is done during a
limited period--from the time the trees are felled until they are
placed in fresh or salt water for transportation to the shipping
points. If, however, the logs are loaded on a vessel direct from the
shore, or if not left in the water long enough to kill the insects,
the latter will continue their destructive work during transportation
to other countries and after they arrive, and until cold weather
ensues or the logs are converted into lumber.

It was also found that a thorough soaking in sea-water, while it
usually killed the insects at the time, did not prevent subsequent
attacks by both foreign and native ambrosia beetles; also, that the
removal of the bark from such logs previous to immersion did not
render them entirely immune. Those with the bark off were attacked
more than those with it on, owing to a greater amount of saline
moisture retained by the bark.

How to Prevent Injury

From the foregoing it will be seen that some requisites for preventing
these insect injuries to round timber are:

1. To provide for as little delay as possible between the
felling of the tree and its manufacture into rough products.
This is especially necessary with trees felled from April to
September, in the region north of the Gulf States, and from
March to November in the latter, while the late fall an