LIBRARY 
RECEIVED 
MONTHLY LETTER OF THE BUREAU OF ENTOMO o&y MAY 25 1933 * 
UNITED STATES DEPARTMENT OF AGRICULTURE DPevariacnt of Agriculture 



Number 227 Activities for February 
(Not for Publication) 



FOREST INSECTS 
spread of southern pine beetle.--For the first time in 40 years 
Dendroctonus frontalis Zimm. has reappeared in epidemic status within 
the most northern limit of its range, according to reports received 
from R. A. St. George, Asheville, N.C. It is known to infest at least 
two counties in southern Pennsylvania, several localities between Wash— 
ington, D. C., and Cumberland, Md., and Fairfax County, Va. Although 
several species of pines have been attacked, virgin shortleaf has prob- 
ably suffered most. Examination of samples from several hundred acres 
of merchantable pine timber near Fairfax, Va., revealed heavy broods 
of the beetle that have successfully overwintered in the trunks of the 
trees. Woodpeckers have worked the mid and upper portions of the trunks 
of many of the trees quite heavily, probably aiding materially in reduc— 
ing the numbers of the pests. The infested trees are believed to have 
been weakened as a result of the drought which has prevailed in this re- 
gion for the past 2 years. Combined with this, mild winters have fa- 
vored insect development, This is regarded as the most notable out- 
break of this beetle in this section since that of 1893. 
Bark beetles in thick—bark pines survive coldest weather.-——J. A. 
Beal and W. J. Buckhorn, Portland Oreg., report that "On February 7 to 
10, upon advice of the Weather Bureau," they "made a trip to the Ochoco 
National Forest and placed mercurial thermometers beneath the bark of a 
dozen trees of varying bark thickness. * * * the temperature, which 
for over a month had stayed above zero, very accommodatingly dropped to 
26 degrees below. Readings were taken every hour for a period of 66 
hours, with a blizzard raging during a portion of this time. At the end 
of 3 days," Messrs. Beal and Buckhorn "returned to Portland with a very 
complete record of subcortical temperatures under varying conditions of 
bark thickness and with different types of infested trees at low air 
temperatures, rarely exceeded in the pine belt of this region." They 
"found a spread in temperature of from 8 to 29 degrees in bark of vary- 
ing thickness and a lag of 1 to 2 hours in the response of bark to 
changes in air temperature. These records show that, even under the low- 
est temperatures known to prevail in the pine region, bark—-beetle 
broods in thick-—bark trees are protected and are able to maintain the 
species." 
Burning in June for control of Douglas-fir beetle spares natural 
enemies.—-W. D. Bedard, Coeur d'Alene, Idaho, in a study of Dendrocto-— 
nus pseudotsugae Hopk. "shows that if control (by cutting, decking, and 
burning the infested trees) could be instituted in June, subsequent to 
the first emergence and attack of this bark beetle, the most important 
