16 College of Forestry 
trunk of Tree I and of others examined in 1915 and 1917, 
but no signs of it were to be found in Tree X. There can 
be little doubt that these insects working in the trunk 
together with a number of borers which typically attack the 
branches and the uppermost parts of the trunk such as 
Neoclytus longipes, Leptostylus sea-guttatus, Pogonocherus 
mixtus, and the three species of Chrysobothris — C. blanch- 
ardi, C. sex-signata and C. dentipes — greatly hasten the 
death of many weakened trees. Melanophila fulvoguttata 
and Phymatodes dimidiatus are two other borers which are 
often associated with them (the latter only in the lower 
trunk) the first of these being a well-known enemy of weak- 
ened spruces and hemlocks. 
However, in the bit of woodland studied, these insects are 
not working unhampered, but natural forces are at hand 
which to some extent at least are tending toward the re- 
establishment of the normal balance of forces and toward 
the return to a more favorable condition for the larch. The 
work of woodpeckers is much in evidence and seems to be an 
efficient agency in reducing to some extent the numbers of 
the brood of several of the more numerous bark-boring 
insects. ‘The birds seem to work in two ways — first by 
making small conical holes through the bark into the sap- 
wood to obtain the larvee of the larger species of beetles 
which have gone there to hibernate or to pupate, and sec- 
ondly by removing practically all of the bark on large areas 
of the trunk to uncover the brood (larvee, pupze and young 
adults) of the bark beetles. 
In some cases this work reached an unusual degree of 
efficiency. For instance one particular tree forty or fifty 
feet high and about 14 inches in diameter, had had nearly 
all of the bark removed from the ground to the very tip. 
(Figs. 5, 6.) This tree had been heavily infested with 
* Dendroctonus simplex, Polygraphus rufipennis and other 
borers, but only a small per cent of the original infestation 
had survived the woodpeckers’ thorough search for food. Of 
course all of the infested trees had not been so thoroughly 
gone over by the birds and a number of such trees had 
