AMEEICAN PLUM BORER. 11 
eating a pupal period in this case of 8 days. Another mature larva 
taken in the field pupated in the laboratory on July 18 and emerged 
July 30, giving a pupal period of 12 days. Two moths emerging in 
the laboratory on July 22 deposited eggs the following day. 
A second generation, or, at least, a partial one, occurs in the lati- 
tude of Winchester. As just stated, one adult emerged on June 22, 
from a larva which hatched in the laboratory on May 7. The indi- 
cated life cycle for the first generation is as follows: Incubation, 10 
days; feeding period, 34 days; prepupal period, 2 days; pupal period, 
10 days; from emergence to egg laying, 1 day; entire length of life 
cycle of first generation, 57.3 days. 
Apparently eggs of the first generation begin hatching in the fore 
part of May and of the second generation about July 1. Whether 
all of the first-brood larvae transform to moths the same season is 
not apparent from the information at hand. It seems fairly certain, 
however, that there is at least a partial second generation. There is 
evidently considerable overlapping of the two generations. Adults 
are emerging more or less throughout the summer and it is possible 
to find at almost any time larvae of all sizes. Pergande, in 1898, 
records rearing one moth in the insectary at Washington from a 
larva sent to him from Anderson, S. C, as late as October 24, and 
the writer has observed newly hatched larvae at Winchester Sep- 
tember 28. 
HIBERNATION. 
In the late fall the larva constructs, under the bark scales at the 
entrance to its feeding galleries, a loose, light, but very tough cocoon 
of white silk. To the outside of this are often fastened frass and 
small pieces of bark. Numerous observations in the seasons of 1912 
and 1913 indicate that many of the larvae go into the winter in an 
immature state, yet in the spring of 1913 no evidences of feeding were 
found among about 100 larvae collected in the field. All of the under- 
sized specimens, of which there were a considerable number, proved 
to be parasitized. In 1912 newly hatched larvae were found in the 
field as late as September 28, and in favorable years immature larvae 
may succeed in passing the winter successfully in northern Virginia. 
In the writer's opinion, however, the mortality due to winter killing 
among the immature larvae must be very high in this latitude. 
When disturbed or exposed to the light the larva leaves its winter 
cocoon and spins up in a more protected place. However, as a rule, 
unless disturbed or unless the winter cocoon is located in an unsatis- 
factory place, the larva pupates in the same cocoon in which it passes 
the winter. Larvae have never been observed passing the winter as 
"free larvae," even parasitized specimens spinning a cocoon. In 
fact, even during the summer months the insect usually threads a 
light shelter at the end of its burrow where it rests when not feeding. 
