48 College of Forestry 
had attacked living trees unaccompanied by the ubiquitous 
P. rufipennis. 
The relations of this bark beetle with the various species 
requiring two years for their life cycle is complicated by the 
fact that the association may be with either the first or the 
second year of the life of these beetles. Our data shows that 
the cerambycid Asemum moestum and the melandryid Ser- 
ropalpus barbatus may be associated with Polygraphus 
during either the first or second year of their hfe history. 
In other words either of these forms may enter the tree at 
least a year earlier than P. rufipennis or may enter during 
the same season. Neither of these would affect the bark 
beetle directly as they are both wood borers throughout their 
larval life. Those which precede it would aid in weakening 
the resistance of the living tree, thus making it a more suit- 
able host for various bark beetles, while those which enter 
at the same time would have little or no either direct or 
indirect effect. 
The large majority of two-year forms, however, enter the 
larch during the same season as P. rufipennis. This lst 
includes the cerambycids — Monohammus scutellatus, Lep- 
tostylus sex-gquttatus, Pogonocherus mixtus, Neoclytus long- 
ipes; and the buprestids, Melanophila fulvoguttata, Chryso- 
bothris dentipes, C. sex-signata, UC. blanchardi and Anthaxva 
quercata. All of these feed under the bark and therefore act 
the réle of robbers by eating the inner bark before the smaller 
bark-beetle larvee can complete their growth. In some cases 
also they may kill the smaller brood outright (Hopkins, 
1899, p. 410) when they by chance meet them under the 
bark. 
The associated predators and parasites are mentioned in 
another connection and it will suffice to say here that the 
predators include Phyllobaenus dislocatus, which appears to 
be ever present in infested larch, Cymatodera bicolor, and 
Podabrus diadema. The parasites include Spathius tomict, 
Spathius sp., Heterospilus sp., Cheiropachus sp., Hurytoma 
sp., Spintherus pulchripenns, a small undetermined ptero- 
malid and the parasitic fly Medeterus sp. 
