Insects Bred from American Larch 37 
hosts, even provisionally, as it was not practicable to identify 
the species with the cocoon (their size being so nearly sim- 
ilar) nor was it possible absolutely to identify the burrows 
in which the cocoons occurred owing to some extent to their 
not having been completed by the dying larva. Therefore 
it is not safe to make any more definite statement than 
that cocoons, which from their size were probably those of 
one or more of these forms, were found both in burrows 
which had been made by P. mixtus and also in other burrows 
made by C. blanchardt. 
Perhaps the most striking difference between the larch 
trunk association and that in the limbs and tops is shown 
when it is stated that the latter includes five buprestids (just 
half of the borers actually taken from thin-barked wood) 
while the trunk association includes but one of this family. 
Thus the buprestids characterize the thin-barked-larch asso- 
ciation and this might well be spoken of as the buprestid or 
flat-headed-borer association. 
All of the borers working in the limbs and tops are bark- 
borers as distinguished from wood borers. By this it is 
meant that the larvee work in the inner bark and outer sap- 
wood, grooving both with their burrows, although making 
their pupal chamber in the wood. One would expect to find 
in such a location in thin-barked wood either very flat borers 
or rather small ones. This perhaps is correlated with the 
fact that such a great per cent of the larvee here are of the 
flathead type and that the remaining forms (P. miztus, L. 
sex-guttatus and N. longipes) are all quite small and of 
slender form. 
Decaying Larch.— No very thorough data regarding the 
later insect inhabitants of dead larch is at hand, but the few 
observations made should be here recorded. From Tree No. 
IV was obtained a piece of root several inches in diameter 
and a foot or more long. This had been dead several years 
as shown by the fact that the wood had begun to decay. The 
bark, however, was still adherent and had served as the 
breeding place for Dryocoetes americanus, the young adults 
of which were found in the inner bark next to the sapwood. 
