268 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 
brown-tail moth, or to the larvse or pupae of the parasite, indiscrimi- 
nately, and in some of the reproduction cages practically every host 
and parasite had been attacked. 
It was not known where these mites came from, but it was pre- 
sumed that they were brought in from the field upon nests of the 
brown-tail moth. By the time that they had been discovered they 
were in practically everything in the laboratory. Even tachinid 
puparia were not immune to attack, and there were numerous 
instances in which the wandering young had forced their way through 
tight cotton plugs, which would ordinarily have prevented the pas- 
sage of bacteria. 
Much time and trouble was necessary before the laboratory was 
finally cleared of the pest; but it was finally accomplished by the 
rigid separation of every rearing cage containing life which had 
been present before the invasion became apparent from those which 
were begun afterwards. The general cleaning up and policy of seg- 
regation proved effective, and by spring the last of the mites appeared 
to have died; nor has a single specimen been observed since. 
As parasites of the brown-tail moth the mites were singularly effec- 
tive. If it were possible to bring about a general infestation of the 
nests in the early fall, it would doubtless result in the destruction of 
a very large proportion of the hibernating caterpillars; but unfortu- 
nately this seems to be not at all practicable. It is not even certain 
that the parasite was actually brought into the laboratory in nests 
of the brown-tail moth, though this would seem to be the most likely 
explanation of its presence. 
The fact that its presence has never once been detected in any of 
the many thousands of similar nests which have been brought in at 
other times indicates rather conclusively that it is not actually an 
enemy of any consequence in the field. 
PTEROMALUS EGREGIUS FORST. 
It was quite late in the spring of 1905 before the senior author was 
able to organize a corps of European collectors, and as a consequence 
only a very small quantity of parasite material was imported during 
t\w summer of that year; but during the fall and winter following, 
well within a year after the work was first authorized by the Massa- 
chusetts Legislature, importation was begun in earnest. More than 
100,000 hibernating nests of the brown-tail moth were received from 
abroad that winter, and since scarcely anything was surely known 
of the parasites which were likely to be reared from them, the early 
discovery of the hibernating brood of Pteromalus egregius (fig. 60, 
p. 263) was hailed with satisfaction. The circumstance has already 
been the subject of comment in an earlier section. 
