PARASITES HIBERNATING TN 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 THE 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 



