17 



when stored in yards and factories. The seasoned and finished prod- 

 ucts, especially those from -apwood. may be infested and destroyed 

 by a number of species of so-called powder-post beetles. Construction 

 timbers and lumber, either before being utilized or while in the struc- 

 ture, are subject to injuries by many injurious and other specie-. The 

 old lumber and timbers of barns and outbuildings, old log and frame 

 dwelling houses, are also infested and injured by forms which are 

 peculiar to such material. 



THE ECONOMIC RELATION OF INSECTS TO IT.RE-T-. 



The preceding references to the insect fauna of forest trees and their 

 products are suggestive of the vast numbers of kinds, groups, and 

 societies of insects and the kind and character of injuries to be studied. 

 This load- as to a consideration of the economic relation of insects to 

 American forests under the varying conditions which prevail before 

 and after the country is settled and its resources developed. 



The relation of injurious insects to the primitivi forests. — The rela- 

 tion of insect enemies of a forest before its resources are available to 

 civilized man is of little or no economic importance. They are simply 

 factors in the general struggle for existence between insects and trees. 

 and between the individuals of the forest community in which the 

 destruction of an individual tree by insects is a benefit to other insects 

 and other trees. If a matured or old tree is killed, it gives more room 

 for the development of the younger and more vigorous ones. The 

 injured, declining, and old individuals furnish breeding places for 

 successive communities of insects, which contribute to their death and 

 rapid decay. Thus the young tree growth is favored by light and 

 plant food, and soon tills up the vacancy. Invasions of destructive 

 insects may cause the death of one kind of tree growth over vast areas. 

 This favor- the enormous multiplication of the insect fauna until the 

 destructive species perishes for lack of food supply, or from the mul- 

 tiplication of its natural enemies. This proves to be a calamity to the 

 other insects which have depended upon the destructive species t<> 

 furnish, in the dying and dead trees, the required condition- for their 

 existence. The dying and dead trees and the fallen and decayed 

 branches, bark, and roots contribute to a more vigorous reproduction, 

 so that the forest found by the pioneer settler ha- lost nothing from 

 ir- insect enemies. 



The relation of the insect enemies of tree- to the pioneer settler in a 

 forested country may be more beneficial than otherwise, so far as his 

 immediate needs are concerned. The forest must be cleared from the 

 land that is desirable for agricultural purposes, and in this process the 

 depredating insects may be decidedly beneficial. They contribute to 

 the death and rapid decay of the girdled tree- in the clearings and 

 hacking.-. Invasions which cause the death of the large timber over 

 TT'.'O — No. 37—0:2 2 



