168 



Insect Ravages in Woodlands. 



bark. But these heroic remedies are practically much beyond our 

 means for successful application in a large way. Fortunately these 

 great invasions do not last many years in succession. They may 

 leave a wide-spread ruin behind them, but some other species of 

 timber tree with fewer insect enemies will come on to supply the 

 place ; and generally the timber killed may still be used for lumber 

 or fuel, if cut within a year or two afterwards. In the case of 

 timber bored into cavities, of course the value is greatly impaired 

 for many uses, and its decay is generally hastened by these causes. 

 668. Where the tree survives the injury of an insect year, the 

 W^S^?-3^^ effect is generally seen in the diminished growth 

 , -.>. .-^ ^^ t\iii,\, season. We have seen in the Museum of a 

 School of Forestry, a section of a tree some hun- 

 dreds of years old, in which for long periods to- 

 gether every third ring of growth was narrow, as 

 we see in one of the rings. in the annexed engrav- 

 ing. This was caused by the eating off of the 

 leaves every third year by a caterpillar. 



669. If the leading shoot of a young conifer is 

 eaten off by insects, or killed from any other 

 *^iurie1i''to'the Leaves <^*"^®' ^'^ growth is checked until another, and 

 Growthcff Wood"*' sometimes two shoots are formed in its place. This 

 gives a defective form, and injures its value. In 

 a lawn or nursery, this damage may be repaired by herbaceous 

 grafting from the terminal shoot of another tree, as elsewhere 

 described. 



670. The damages done by insects to a forest are sometimes im- 

 mense. In recent years the spruce timber in New Brunswick, 

 Maine, and Northern New York has been thus destroyed to the ex- 

 tent of millions of dollars in value. 



671. Kaltenbach, an approved European writer upon Forest 

 Entomology, enumerates 537 species of insects injurious to the oaks, 

 107 to the elms, 264 to the poplars, 396 to the willows, 270 to the 

 birches, 119 to the alder, 154 to the beech, 97 to the hazelnut, and 

 88 to the hornbeam. Of coniferous trees, the pines, spruces, larch, 

 and firs are fed upon by 299 species, and the junipers by 33. 



672. In the United States, while many observers have given 

 their attention to this branch of natural history, much still remains 

 to be known upon this subject, especially as relates to the geograph- 



