38 THE SCOLYTID BEETLES. 
mendations submitted. But, through the lack of public appreciation 
of the importance of the problem at the time, and the lack of sufficient 
authority and funds later, it was allowed to extend beyond practical 
control, and in consequence a large percentage of the timber on the 
entire National Forest has been killed. 
DETAILED INFORMATION ON THE SPECIES. 
The discussions on the following pages relate to more detailed 
information on each species. 
In the first paragraph, under the English and technical name, will 
be found a brief summary of the distinctive characters of the species, 
its seasonal history, habits, distribution, and evidences of attack. 
This is to facilitate preliminary identification by the reader, and is 
followed by a more detailed account of the seasonal history, habits, 
and economic features as a basis for the recommendations and proper 
application of methods of control, and closed with references to the 
investigations and identifications on which the statements are based. 
The fact that the species are discussed more or less independently 
necessitates some repetition of statements relating to seasonal his- 
tory, habits, and methods of control. In view of the fact, however, 
that a bulletin of this kind is used mainly as a reference work, in 
gaining information on a special insect or subject, as it is required, 
such repetitions are to a certain extent necessary. 
GENERAL EXPLANATION OF DESCRIPTIVE AND OTHER TERMS. 
While the illustrations will show the parts designated by technical 
or semitechnical names, there are other terms used in the discussion 
of seasonal history, habits, etc., which may need some explanation 
for the general reader. 
Brood. — The term " brood" refers to the progeny of a single pair, 
or the individuals hatching from the eggs in a single egg gallery. 
Generation. — By a " generation" is meant all of the broods that are 
the offspring of the adults of the overwintering broods, except the 
overwintered parent adults, which may be parents of the overwin- 
tered broods, and also of broods from eggs deposited by them in the 
spring. Another exception is in the retarded individuals which pass 
more than one winter in either the larval or adult stage. 
All the progeny of the overwintered broods may be said to com- 
prise a complete generation. If all of this progeny complete their 
development between the time the first eggs are deposited in the 
spring and the close of the same season of activity, and emerge from 
the trees, it may be referred to as constituting a complete seasonal 
generation. If another set of broods develops to maturity from eggs 
deposited by the adults of the first generation of the season, it will 
form a complete second generation, and so on. If, however, only 
