4 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
Some of these, such as the gypsy moth, the European pine shoot moth, 
and the European spruce sawfly, are among our most serious forest 
pests. 
PREVALENCE AND ACTIVITY OF FOREST INSECTS 
The abundance of individuals of an insect species 1s never constant, 
but varies greatly from time to time. Some injurious species, as the 
southern pine beetle, are at times so rare, even during their active 
season, that a singlé individual can scarcely be found in the for est, and 
yet a few months later there will be literally millions of them ina 
limited forest area. Great outbreaks of the spruce budworm in the 
Northeast occur only at long intervals. Other species, as the Colum- 
bian timber beetle, ‘working in the sapwood of living trees, may be 
more or less static, causing a small amount of injury e ‘each year for a 
century or more. General. discussions of forest insects and their rela- 
tion to the trees will be found in the following publications: Doane 
. (133), Graham (194), Keen (262), Fitch (758), Craighead 
(775), and Chamberlin.* 
DESTRUCTION OF STANDING TIMBER 
Notable outbreaks of forest insects have from time to time taken a 
tremendous toll in our forests. In the Eastern States the greatest dep- 
redations to mature timber have been caused by bark beetles of the 
genus Dendroctonus and a few defoliators. 
The southern pine beetle is the most destructive eastern bark beetle, 
killing all species of pine from Maryland and Virginia west to the 
Ozarks, and south to the Gulf of Mexico. One of the earliest recorded 
outbreaks centered in Virginia and West Virginia about 1891. A great 
quantity of spruce was killed, as well as enormous numbers of pines. 
Other widespread outbreaks occurred in the Carolinas and noes la in 
1910 and 1911 and in Virginia and North Carolina in 1922 and 1923. 
Lesser and more localized outbreaks developed 1 in 1925, 1926-27, and 
1930-31 in north-central Virginia, where 5 million board feet were 
destroyed on one holding, and again in 1936, 1937, and 1938 there 
was an outbreak that caused the destruction of some 10 million board 
feet of loblolly pine in northeastern Virginia on two lumber com- 
panies’ holdings. 
Depredations in mature stands of spruce in the Northeast, assumed 
to have been by the spruce bark beetle, were reported as far back as 
1830. From that time to the present there are records of repeated 
clestruction of this tree species in the forests of Maine, New Hampshire. 
and Vermont. A particularly extensive outbreak of the beetle occurred 
from about 1897 to 1901 in New Hampshire and Maine and was inves- 
tigated by A. D. Hopkins during the latter part of this period. Little 
evidence of destructive activity of this beetle occurred a gain until 1936 
and 1937, when 5 or 6 million board feet of spruce was destroyed in the 
Green Mountains alone. Unfortunately the records of these outbreaks 
in eastern forests are not accompanied by accurate figures of losses. 
“CHAMBERLIN, W. J. THE BARK AND TIMBER BEETLES OF NorTH AMERICA NORTH 
OF Mexico. THE TAXONOMY, BIOLOGY AND CONTROL OF 575 SPECIES BELONGING TO 72 
GENERA OF THE SUPERFAMILY SCOLYTOIDEA, Oreg. State Col. Coop. Assoc., 513 pp. 
1939. [Processed. ] 
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