48 College of Forestry. 
a new host. Some, however, coming from the same colon- 
ies but from eggs laid later, may not emerge before August 
10th. These then may be an entire month behind the earlier 
ones of their generation. This causes some overlapping of 
the broods even from the same ancestry and more than 
casual field study is necessary to get at the true conditions. 
The brood arising from the earlier individuals of the 
second generation, reach maturity carly in September and 
some of them emerge and excavate new brood burrows, 
although the majority pass the winter as adults in the larval 
host. The offspring of those of the second generation which 
emerge, pass the winter as half-grown to full-grown larvae, 
while the parent beetles themselves occasionally survive the 
winter. 
The beetles of the first generation emerging in August, 
attack new hosts and their offspring pass the winter as 
young adults, pupae or full-grown larvae. The great 
majority of the second generation reach maturity (by which 
is meant sexual maturity acquired after feeding a week or - 
two in the larval host) so late that the weather conditions 
cause them to remain in their larval host all winter, thus 
completing exactly two generations. 
Those which pass the winter as larvae or pupae either of 
the second or third generation, do not emerge until late in 
May or during June of the following season. These cer- 
tainly do not produce more than two generations and most 
of their descendents pass the succeeding winter as adults of 
the first complete generation. Even in normal seasons, a 
considerable number do not reach maturity and these winter 
as full-grown larvae or pupae, while in years when the 
cold weather sets in earlier than usual, a large percentage 
hibernate in an immature condition. 
No detailed observations with the special purpose of 
determining the per cent of each of the stages represented 
which pass through the rigors of winter weather successfullv 
were made. However, data collected in a more or less casual 
manner would indicate that all staves beyond the half-grown 
larvae are about equally successful except the callow or 
