Insects Bred from American Larch 65 
packed with fine, dust-like frass. Winter is most usually 
passed either in the larval or adult stage. 
One year is usually required in this locality for the com- 
pletion of its life history. However, it should be realized 
that this represents only the normal condition in the locality 
in which this form was studied (Crittenden and Syracuse). 
It 13 quite likely that it may occasionally, or even may 
usually, require two years for its development in the colder 
regions of the State. Dogmatic statements regarding the 
length of larval life are dangerous. Adults emerged May 26, 
31 and June 8 and 15, 1916, from larch killed during 1914. 
The eggs of P. dimidiatus had doubtless been laid in 1915, 
as was shown in one case by the relation of the larval 
burrows of this species to the engravings of P. rufipennis 
occurring in the same material. 
P. dimidiatus may be preceded in the bark of larch by 
several insects, notably by P. rufipennis mentioned above, 
by Dendroctorous simplex, Eccoptogaster picew and by Ase- 
mum moestum. On the other hand, it may in other cases enter 
the tree during the same season as any or all of these. It 
seems rather to prefer trees (whether spruce or larch) which 
are thoroughly dead, and, therefore, when any of the above 
species precede it in the bark they by so doing benefit rather 
than injure it as a place of breeding for P. dimidiatus. On 
the other hand, where the larvee of this cerambycid occur in 
the same material as the brood of the various scolytids men- 
tioned, it may be injurious to the latter by robbing them of 
their food.. Other borers which have been bred from the 
same material include the cerambycid Leptostylus seax- 
guttatus, the melandryid Serropalpus barbatus, and the two 
siricids Urocerus albicornis and Sireax abbotit. 
Two predators, Phyllobaenus dislocatus and Cymatodera 
bicolor, were associated with P. dimidiatus. The parasites 
derived from the same material include Rhyssa lineolata, 
Pseudorhyssa sp., Odontaumerus canadensis, Hurytoma sp. 
‘and three apparently new species of Doryctes. The rela- 
tions of these parasites have previously been discussed 
3 
