INSECT ENEMIES OF WESTERN FORESTS lead 
larvae do not have time to complete their development before cold 
weather overtakes them in the fall, and consequently they are obliged 
to spend another winter in the host tree.’ One generation of beetles 
ee ee error _ecct[.CO_ EOL Ow OO Ea____ ea 
FIcuRP 59.—Galleries of the Douglas fir beetle on inner bark surface. 
a year is probably the normal rate of development, but there are 
considerable overlapping and retardation of broods, somewhat obscur- | 
ing the demarkation between generations. 
