168 PRACTICAL. FORESTRY 
fever are carried from person to person by these in- 
fected insects. 
We should encourage the enemies of injurious 
insects, such as bats, toads, snakes, lizards, birds, fish, 
and useful insect-eating insects. We should encour- 
age beneficial birds by preventing the depredations of 
that most noxious of all animals—the man with the 
gun. 
The cleaner the woods the fewer the breeding- 
places of insect pests. The greater the mixture of 
trees, the less will be the damage. 
It is impossible to do in forestry what is done 
in horticulture in case of the visitation of an insect 
pest. If the forest is infested in spots, and there is 
danger of the spread of the disease, it is best to eut 
down the wood, utilize as much of it as possible, and 
then burn the rest. 
Trees with weakened vitality fall an easy prey to 
insect pests, although healthy, vigorous trees are 
sometimes infested. Some borers are drowned in 
the sap of healthy trees, so that trees which are 
sickly, or which have been injured by fire, are first 
attacked. 
Certain species of insects are often reduced in 
numbers by the use of decoy trees. Trees which are 
crooked and of little use are girdled. Insects, espe- 
cially borers, are attracted to the dying tree, and when 
