10 Farmers’ Bulletin 1197. 
on which to lay their eggs. During certain periods, however, their 
number is almost negligible. 
The roundheaded borer has two generations a year and two periods 
during which the beetles are abundant. The overwintering forms 
mature and the adults emerge and fly chiefly during March and 
April. From these originates the summer generation, which de- 
velops in five months, the beetles emerging in August and September. 
The powder-post borers fly as adults more or less during the entire 
year, although during November, December, and January very few 
are to be found. The medium and the smaller forms are most abun- 
dant from April to September, and during this time they develop 
very rapidly, producing two or three generations a year. During the 
hot part of the summer adult beetles develop from eggs in 60 to 70 
days. The large powder-post beetle is active from July to September, 
having only one well-defined generation in a year. 
The flat-headed borer flies about from March to October, being 
most abundant in April, May, and June. There is apparently only 
one main generation a year, although some develop more slowly 
than others, thus extending the period during which the beetles fly. 
CONDITIONS FAVORABLE AND UNFAVORABLE FOR 
ATTACK. 
The large powder-post beetle prefers wood which has dried out 
for several months, but all the other borers show a decided preference 
for freshly cut wood on which to lay their eggs. Some exceptions 
have been noted, but this is the general rule. Wood which is cut 
in the fall and seasoned during the winter months is very unattrac- 
tive in the spring months when the beetles are flying about in search 
of suitable material for the development of their broods. 
It has also been found that only the underside of logs or branches, 
or those pieces of wood not in the direct sunlight, are selected for 
feeding. During the greater part of the year the sun heats the 
upper surface so much that it is impossible for anything to live on it. 
METHODS OF PREVENTING INJURY. 
Upon a knowledge of the habits and seasonal activities of these 
insects must depend any method for combating them. It has been 
shown that during certain seasons of the year few of these insects 
fly about, that they do not like seasoned wood, and that they can not 
live beneath bark exposed to direct sunlight. Taking advantage of 
these factors, the following methods have been tried for preventing” 
damage by them and have proved very successful for all practical 
purposes, 
eee oe 
