PARASITES HIBERNATING IN BROWN-TAIL WEBS. 261 
enough for a satisfactory colony were reared, and again it was at- 
tempted to hold the brood over winter in cold storage, and again the 
attempts failed. 
If judgment is based upon the percentage of parasitism by this 
species in the lots of egg masses of the brown-tail moth which have 
been received from abroad, it is an unimportant parasite in Europe. 
Partly on this account, and more, perhaps, because it was colonized 
so satisfactorily in 1907, no further attempts to secure its introduction 
into America have been made. Neither has a serious attempt to 
recover it from the field in the vicinity of the 1907 colony site been 
made, and it may have become established from this colony. 
The plans for field work in 1911 include the collection of a large 
number of eggs of the brown-tail moth from the general vicinity of 
the larger colonies of 1907 and, if arrangements can be perfected, for 
a study of the extent to which the eggs of the brown-tail moth are 
attacked by parasites in Europe. As in the case of every other class 
of parasite material received at the laboratory, nothing is known of 
the circumstances under which those egg masses which were received 
from 1906 to 1908 were collected. It may easily be that they were 
collected too soon following their deposition to permit of their having 
been parasitized to anything like the extent which would have come 
about had they been allowed to remain in the open for a few days 
longer, and in at least one instance the receipt of the masses with a 
dead female moth accompanying each was sufficient to more than 
justify such doubts. 
PARASITES WHICH HIBERNATE WITHIN TH WEBS OF THE 
; BROWN-TAIL MOTH. 
Partly because it has been practicable to import the gipsy moth 
and the brown-tail moth in the hibernating state in better condition 
than it has been possible to import their active summer stages, but 
equally because there has been ample time and opportunity to study 
them during the winter months when only a limited amount of field 
work could be done, it has been possible to learn more of the parasites 
which hibernate within the gipsy-moth eggs and the nests of the 
brown-tail moth than of those parasites which are only associated 
with the same hosts during a more or less limited time in the summer. 
The winter nests of the brown-tail moth have from the beginning 
been the subject of an increasingly intensive study, and as a result 
more is known of the parasites which hibernate within them than of 
any other group of brown-tail moth or the gipsy-moth parasites with- 
out excepting even the parasites of the gipsy-moth eggs. 
Very large numbers of these nests, amounting in the aggregate to 
more than 300,000, have been imported each winter from that of 
1905-6 to that of 1909-10, inclusive, Now that all of the primary 
