34 
different from the periods, that may in the future be observed, for 
the egg where pup and eggs are subject to the same atmospheric and 
other conditions. 
Present knowledge indicates that the number of generations that are 
normally produced each year is two in the most northern range of 
this species (in years when it develops northward), three for central 
localities like central and southern Illinois and the District of Columbia, 
and probably four for the extreme South. We know, however, prac- 
tically nothing of the development of this species in the Gulf States. 
Hibernation, according to recent observations in the District of 
Columbia, takes place exclusively in the pupal state, and it seems 
probable that this is so elsewhere. The reasons for this statement are 
that eggs deposited in late autumn have invariably hatched, and that 
pup kept in the nearest obtainable natural conditions have not devel- 
oped moths during winter. In a more favorable environment farther. 
south hibernation would, without much doubt, have been successful, 
and the moths would have issued early in spring. Furthermore, had 
moths been obtained during winter from material under our observa- 
tion it does not seem within the bounds of possibility that any would 
have sustained life in our variable climate. 
NATURAL ENEMIES. 
It has been stated with reason that there is perhaps no prominent 
injurious insect, at least none of the periodically destructive species, 
in whose economy natural enemies play so important a part as the 
common army worm; and this is toa certain extent true of quite a 
number of other pests with similar habits. It was natural to expect, 
therefore, that the fall army worm might, at least in its latest appear- 
ing generations, fall a prey to some naturalenemy. For some reason, 
however, these natural checks did not materialize to any extent, at 
least with the exception of birds they were not at all active during 
the year of this outbreak in the vicinity of the District of Columbia. 
A different condition of affairs, however, obtained in some other 
localities. 
ENEMIES OBSERVED DURING 1899. 
Soon after the outbreak of caterpillars was first noticed on the 
Department grounds in 1899 afew English sparrows were observed on 
the infested plats; their numbers increased daily, and there is no 
doubt that in this particular place they depleted to a very consider- 
able extent the numbers of this insect as well as ef the others which 
were concerned in the injury. The sparrows were actually observed 
by Dr. Sylvester D. Judd, of this Department, in the act of devouring 
the larval fall army worms. 
