32 College of Forestry 
guttatus, on the other hand, most commonly breeds in the 
tops and limbs when it infests larch. There can be little 
doubt that it prefers the thin-barked parts of the tree. 
The melandryid Serropalpus barbatus is the wood-boring 
insect most often found in and most characteristic of injured, 
dying, or recently dead larch. It was bred in considerable 
numbers from Trees I, V, VI, VII, and X. The larvae are 
‘wood-boring inseets which live two or possibiy more seasons 
in the sapwood or heartwood. This species is found through- 
out the trunk, but is most common in the lower trunk below 
the lowest branches. 
The siricids Urocerus albicornis and Sirex abbotu occur 
more or less throughout the trunk even up among the 
branches. It is probable that they may even breed occasion- 
ally in the larger branches. However, these forms are all 
typically inhabitants during the larval state, of the wood of 
the part of the trunk free of limbs, as is shown by the fact 
that of twenty-five specimens of the two species bred from 
larch, all but four were from the tree below the level of the 
first still adhering lmbs. 
There are several parasites which were bred from wood or 
bark containing one or more or these borers. These include 
Ehyssa lineolata, Pseudorhyssa sp., Odontaumerus cana- 
densis, and three species of Doryctes, all of which are appar- 
ently new. ‘These six species, four of which are new, were 
derived from three distinct lots of material in three separate 
breeding cages. They were associated with P. dimidiatus, 
M. scutellatus, L. sex-guttatus, A. moestum, S. barbatus, 
the two predators Phyllabaenus dislocatus and Cymatodera 
bicolor and with Tenebrio tenebriodes and Dryophthorus 
americanus (the latter two inhabiting dead and partly 
decayed wood in one of the lots). However, of these numer- 
ous wood and bark-inhabiting forms only two (P. dimidiatus 
and S. barbatus) were derived from all three lots, thus estab- 
lishing the probability that one or both of them served as 
hosts for these parasites. 
A later detailed study of all of the material in these lots 
was made with very interesting results. When the bark was 
