THE GENUS DENDROCTONUS. 33 
attention. While in exceptional cases it may be advisable to have 
laws governing the treatment of timber infested with a dangerous 
pest, such laws should be based on expert advice and should apply 
to the more extreme and well-known cases only as a last resort. It 
is probable that in most cases legislation will not be necessary, and 
that more ultimate good will result without than with such laws, 
especially when it can be made clear to the owner that his personal 
interests demand that he take the proper action and that when nec- 
essary his neighbors will render assistance, as is done in the case of 
a forest fire. 
INACCESSIBLE AREAS. 
There are yet large inaccessible areas in the East and West where 
it will not be practicable or possible to control the depredations by 
these beetles, and which therefore must be left to natural adjustment. 
While under natural control the matured timber will be lost, it will 
usually be replaced by young growth, so that under normal conditions 
the forest will be perpetuated. Under exceptional conditions and 
combinations of detrimental influences, such as insects, fire, and 
drought, extensive areas may, however, be completely denuded, never 
to be reforested under natural conditions. This has doubtless hap- 
pened in very many denuded and bare areas in the Rocky Mountain 
region, which were at one time heavily forested. 
TRAP-TREE METHOD OF CONTROL. 
The well-known attraction of many species of European barkbeetles 
to weakened, dying, and felled trees suggested to some of the earlier 
writers on forest insects a method of barkbeetle control which since 
that time has been widely recommended and under certain conditions 
and for certain species of beetles has be'en successfully practiced. It 
is the so-called trap-tree method, in which living trees are deadened 
or felled at the proper time or season to attract the insects and induce 
them to breed in the bark, where they can be easily destroyed by 
removing the latter or burning the entire tree. Experience and 
observations indicate, however, that while this method is successful 
in attracting many species of bark and wood boring insects it does 
not always attract those which are the most destructive to the living 
trees, or at least not in sufficient numbers to justify its general recom- 
mendation and adoption. 
Among the Dendroctonus beetles there are a few species which are 
attracted to weakened and dying trees and to the stumps, logs, and 
tops of recently felled living trees. These are species 1, 2, 4, 12, 13, 
22, and 23 and, to a more limited extent, species 14 and 15, but ex- 
tensive experiments have indicated quite conclusively that the Black 
Hills beetle, the most destructive species of all, can not be success- 
89535— Bull. 83, pt. 1—09 i 
