300 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
East as in the West, a number of them are serious pests. One reason 
why the losses are not so great is that the East no longer contains many 
large tracts of overmature trees in which an extensive outbreak can 
develop. In the West vast forest tracts, consisting largely of one kind 
of tree and often containing many mature, overmature, and decadent 
trees, offer ideal habitats for certain bark beetles. Under proper cli- 
matic conditions these beetles may rapidly increase to outbreak 
proportions. 
All stages of the tree, from the origin of the seed to the utilization 
of the lumber, are subject to injury by scolytid beetles. Injuries may 
be considered under several headings as follows: (1) Damage to forest 
reproduction; (2) impairment of the health and growth of trees; (3) 
actual killing of trees; (4) injury to timber during the process of 
lumbering and manufacture; and (5) damage to utilized timber. 
Injuries to utilized timber by bark beetles is of much less importance 
than that by other groups of insects, such as lyctids and termites. 
Aside from damage by tropical ambrosia beetles of the genus X yle- 
borus to barrels and other wooden containers of water, wine, or other 
liquids, bark-beetle damage is practically confined to timber from 
which the bark has not been removed. Fence posts, poles, and round 
structural timbers more or less in contact with the soil, from which 
they can obtain moisture, are subject to injury by ambrosia beetles 
during the first year of this use—especially if used without previous 
seasoning. The burrows extend in through the sapwood, and those 
of Platypus even into the heartwood, thus reducing the strength of 
post or pole and allowing ready entrance to decay-causing fungi. At 
least one wood-eating scolytid, Hylocurus langstoni Blkm., is capable 
of doing considerable damage to unbarked timbers, its injuries being 
somewhat similar to those of the powder-post beetles. 
A host of bark beetles and ambrosia beetles prefer to breed in re- 
cently cut trees. Therefore in the warmer seasons many trees become 
infested within a few days after they are cut. The injury to such 
material by the true bark beetles is not great, since they merely destroy 
the inner bark; but, unfortunately, many species of bark beetles intro- 
duce into the tree the spores of wood-staining fungi, such as the blue 
stains. The hyphae of these penetrate the sapwood and discolor it, 
rendering it unfit for many purposes and reducing its sales value. 
The bark beetles, by loosening the bark, permit more ready entrance 
for fungi. 
The burrows of ambrosia beetles, however, are extended directly 
through the bark and into the sapwood, where they are branched or 
var iously elaborated, according to the species concerned. ‘The am- 
brosial fungi, on which both larvae and adults feed, grow in the bur- 
rows and impart a black stain to the surrounding wood. The burrows 
of most ambrosial beetles are confined to the sapwood, but species of 
Platypus extend theirs also into the heartwood. Unless it is promptly 
sawed up, timber cut during the warmer months will invariably suffer 
from ambrosia beetle attack. In the Southern States lumbermen 
know from experience that it is wise to work up oak, gum, and cypress 
cut during the warmer months within 2 or 3 weeks from the time it is 
felled. Within that time many burrows may already have been 
started, but they will penetrate only a short distance and most of them 
will come off in the slab when the logs are sawed into lumber. 
