54 College of Forestry 
larval burrows of scolytids of their small size. The data 
tabulated below will give the facts obtained by a careful 
measurement of forty larval mines: 
Mininrum lene thy oip larval burkowsree aa eerie 58 mm. 
Maxamimelenoth vot lanyallaibimerOwin mere itl) ea eile 103.) mm. 
Average lencth of lanvall bULEOWeM ae oe ec iae cies 75.8 mm. 
Of the forty burrows measured nineteen were between 60 
and 79 mm. long, ten were less than 70 mm. long, three 
were between 80 and 89 mm. long, five were between 90 and 
99 mm. long, and three were more than 100 mm. long. 
The same beetles are associated with H. picew as with 
P. rufipenmis with the exception of those found typically 
only in the lowermost part of the trunk. These include 
Dendroctonus simplex, Monohammus — scutellatus, and 
Asemum moestum. Of these probably the latter is the only 
one which would not likely to be associated with LH. picee, 
as it is found only a few feet at most from the ground. 
EH. picee is found more often associated with P. rufipennis 
than with any other insect. The latter starts its burrows 
somewhat earlier in the season and naturally when it is 
present in numbers sufficient to occupy all or nearly all of 
the bark of the entire trunk the presence of its brood often 
very much limits the available breeding places of the former. 
Thus, in most of the trees studied H. picew had been thus 
excluded from the trunk even well up in among the branches 
and was not found except in the tops and in the less desirable 
limbs. In other cases where the earler infestation of the 
P. rufipennis was not so heavy, the two small scolytids were 
found associated in the upper, middle and even to some extent 
in the lower trunk. In such cases it is interesting to observe 
that the brood of H. picew becomes more and more numerous 
in the upper trunk as that of P. rufipennis becomes less so. 
Of the other associated borers the relations with the five 
species of buprestids which are characteristic of the insect 
association in the tops and limbs are perhaps most close. 
These in their relation to H. piceew must be classified as 
robbers, it being understood that this relation on the part 
