20 



of commercial products. Their burrows cause defects in the wood, and 

 are the means of .starting* decay, which renders the heartwood worth- 

 less for commercial purposes. The living Hark may be attacked by 

 bark-boring grubs in sufficient numbers to seriously affect its vitality, 

 so that it will soon succumb to the attacks of other insects or diseases. 



The mature tree suffers most from the many wood-boring beetles 

 and grubs. The destruction of some of the larger roots by the great 

 root borer causes dead branches and dead tops. The borings of the 

 carpenter avoith and other borers in the main trunk, top. and larger 

 branches result in rapid decay, hollow trunk, and generally worthless 

 condition, while its weakened vitality makes the tree an easy prey to 

 destructive bark-boring enemies. The trees blown down by storm or 

 felled by the ax are attacked by a vast number of species of insects. 

 Some live in the bark, where they do little or no harm to the commer- 

 cial product, but certain kinds may thus multiply rapidly and attack 

 the standing timber. The wood, however, may be seriously injured 

 by many species of wood-boring beetles and grubs which breed only 

 in the wood of dead and felled trees. 



Old dead, standing, and felled trees and old logs and stumps are 

 infested by many insects which not only contribute to the rapid 

 destruction of the wood, which otherwise might have some commer- 

 cial value, but certain kinds breed in such material and emerge to 

 attack the wood of recently felled trees and injured places in the 

 standing living ones. They also attack square timbers in bridges, 

 trestles, railroad bed, etc. 



SOME OF THE PRINCIPAL INSECT DEPREDATIONS IN THE FORESTS OF 

 THE UNITED STATES. 



THE PINES. 



Between 400 and 500 species of insects are known to inhabit the 

 living, dying, and dead pines of the United States. The pine forests 

 of the East, Northeast, and Southeast have suffered and are now suffer- 

 ing greatly from the ravages of destructive bark-beetles. A few years 

 ago (1890-189*2) a trouble spread over an area of 75,0<>o square miles 

 in the Middle Appalachian region w r hich resulted in the death of mil- 

 lions of pine trees. This included all of the indigenous and some of 

 the introduced species in the forests, private grounds, and parks. 

 Upon careful investigation, this trouble was found to be caused pri- 

 marily by the ravages of a single species of bark beetle [Dendroctonus 

 frontalis Zimm. A~ar. destructor Hopk.). Previous to 1890 this was a 

 rare insect in collections, and nothing was known of its habits. It 

 disappeared and the trouble ceased in 1893. This insect is liable to 

 appear again in destructive numbers. It is therefore of the greatest 

 importance that special efforts be made to determine the sections in 

 the Eastern and Southern pine forests where it may yet survive, so 



