Insects Bred from American Larch 35 
which are more suitable for many forms than are to be found 
in other parts of the tree. This is indicated by the fact that 
five species of borers were obtained exclusively from tops 
and limbs while a number of other species taken from other 
regions occur also in the thin-barked parts. Of these latter 
two in particular show a decided preference for the newer 
growths. 
Most of these forms which characteristically inhabit thin- 
barked regions are species requiring two years for the com- 
pletion of their growth. During the second summer of this 
period the moisture conditions in the thin-barked parts are 
strikingly different from that existing in the thick-barked 
regions. Indeed it is hardly conceivable how the bark or 
sapwood here can be of use as food during times of drought 
when these parts are apparently dessicated, and indeed it 
may well be that during such periods the larva ceases feeding 
and becomes more or less torpid. But however that may be, 
it is a fact that regions showing such conditions are appar- 
ently sought by a considerable number of species in prefer- 
ence to other parts of the tree where moisture conditions are 
different. Other factors may enter into this choice and it is 
possible that these may determine the beetle’s choice of 
breeding places, but our data seem to indicate that this ques- 
tion of lack of excessive moisture is one of the determining 
factors. This apples not to the forms requiring only a single 
year for their life cycle, but to those which remain under the 
bark for two years. 
A total of ten species of boring beetles were bred from 
thin-barked larch. This includes two scolytids, three ceram- 
byeids and five buprestids. The scolytid most characteristic 
of larch limbs and tops is Hccoptogaster piceae. This seems 
to be its favorite breeding place and study of old engravings 
shows conclusively that there is a larger percentage of larve 
reaching full growth here than in the trunk region. This 
is especially true of the tops of a diameter of from 114 to 
31% inches, although the larger limbs also offer favorable 
conditions. The other scolytid P. rufipennis, while often 
numerous in the tops and occasionally in the limbs is typi- 
