FOREST INSECTS. 



73 



quantities, often living for moutlis on little else, and 

 sheep are destructive in the same way. Hogs also find 

 a living- in the forest, but they are less harmful, 

 because a large i)art of their food consists of seeds and 

 nuts. East of the Great Plains very large numbers of 

 cattle and hogs are turned into the woods, but sheep 

 grazing in the forest is most widely developed in the 

 West, and especially in California, where it should be 



Fig. 67. — Larch trees killed by the larva of a small sawfly. The land has just 

 been lumbered for Spruce. Adirondack Mountains, Xew York. 



prevented altogether, in Oregon and Washington, where 

 it should be regulated and restricted, and in some 

 interior regions, like Wyoming and Xew JMexico, where 

 it should be rigidly excluded from all steep mountain 

 regions, and carefully regulated on more level ground. 



FOREST IIS'SECTS. 



Insects are constantly injuring the forest, just as year 

 by year they bring loss to the farm. Occasionally their 



