470 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
results were as follows. In many cases the burrow was started but was 
abandoned before eggs were laid. In other cases the egg-galleries were 
continued for some distance, although always short and a few eggs were 
laid. The larvae hatching from the eggs were for the most part soon 
overcome by the excessive amount of moisture set free into their bur¬ 
rows as these were excavated by the larvae. The mortality of the adults 
and larvae in the later burrows was much heavier than in those started 
during July because of the greater saturation of the soil, the greater 
amount of cloudiness and the consequently greater excess of water in 
the plant tissues. 
If the truth of the hypothesis advanced should be established by 
future detailed and systematic observations, of what practical use would 
it be to forestry? To the writer it seems that it promises to be of great 
practical value. While it is manifestly impossible for man to so change 
climatic conditions as to control an infestation once thoroughly es¬ 
tablished, a thorough knowledge of the causes underlying the develop¬ 
ment of a bark-beetle epidemic and a full appreciation of the factors 
favoring the incidence of such outbreaks, will give to those responsible 
for the protection of the forests the ability to foresee a possible epidemic 
before this has really started. Thus, if it is known that a period of 
deficiency in rainfall at certain seasons weakens the resistance of trees to 
attack and at the same time favors the development of certain tree de¬ 
stroyers, an intelligent lookout may be made for the first signs of an 
undue increase in the known destructive agencies and these can be 
controlled by means of already known methods long before the infes¬ 
tation reaches epidemic proportions. 
Even when, as is often the case, the meterological data for a given 
locality is lacking, there would seem to be an excellent chance of de¬ 
tecting adverse conditions due to a deficiency in rainfall or to other 
influencing factors, by a systematic study of increment borings. If a 
majority of these show a marked lessening of increment growth over a 
period of several years, an especial attempt may be made to detect a 
developing infestation before it becomes epidemic. Such an incipient 
outbreak can then be controlled before it becomes serious and thus 
prevent great possible damage. In other words, if taken in time pro¬ 
phylactic measures may be used rather than remedial measures. 
