130 FIRST BOOK OF FORESTRY 



the diseases are due to ordinary fungus plants, similar 

 to those which kill our house flies in the fall of the 

 year, when they may be seen clinging to window panes, 

 surrounded by a ring of dustlike spores (seeds of fungi). 



Insect pests in pine and spruce are usually much more 

 serious than in hardwoods, since conifers generally are 

 not so resistant as the broad-leaved trees. If the leaves 

 of a pine tree are eaten off, it is quite sure to die ; while a 

 maple may survive though it loses its leaves two seasons 

 in succession. 



From what we have learned it is clear that the leaf- 

 eating insects help the bark beetles, and also that these 

 latter are favored wherever the forest trees are injured by 

 storm and snow or by fire, and even when they are in a 

 weakened condition from poverty of soil or lack of mois- 

 ture. Thus, things are very apt to go from bad to worse, 

 even in the woods. 



Mammals. Of the larger animals it is chiefly the 

 rodents mice, rabbits, and squirrels and also the 

 grazers deer, sheep, goats, and cattle which become 

 injurious in forests. 



The mice and rabbits injure young trees by gnawing 

 the bark ; mice and squirrels eat the seeds ; while the 

 grazing animals browse off the leaves and green shoots 

 of young trees and thus cripple and often destroy them. 

 Where cattle and sheep go in larger numbers, or where a 

 small flock has the run of a small wood all summer, they 



