PARASITES HIBERNATING IN BROWN-TAIL WEBS. 289 
of which came from hibernating caterpillars, but a part of which was 
imported as parasites of the full-fed and pupating caterpillars. The 
experiment of colonizing large numbers of retarded caterpillars in the 
vicinity was repeated, and with similar results to those secured in the 
previous season. 
In 1910 a larger number of the cocoons was found, but at the 
same time a very few were secured from the caterpillars which had 
been collected in the vicinity of the colony. It did not look as though 
much was to be expected from the parasite at first, but when, toward 
the end of June, collections of full-fed caterpillars were made from 
various localities for the purpose of determining the status of the 
tachinid parasites, the results were much more encouraging. Cocoons 
of the second generation of Meteorus were soon found in some num- 
bers and to a distance of a mile or more from the original colony 
center. Within a rather limited area near the colony center they 
could almost be said to be abundant, so abundant that 50 were col- 
lected in the course of about two hours’ work. They are far from 
being conspicuous objects, being wholly disassociated from the cater- 
pillar which served as host, and on this account the number collected 
was considered to indicate a very satisfactory abundance. 
Its rate of dispersion, so far as indicated by the results of the 
summer work upon the caterpillars of the brown-tail moth, was too 
slow to be satisfactory, but in the early fall a single specimen, defi- 
nitely determined by Mr. Viereck as of this species, was secured from 
a lot of caterpillars of the white-marked tussock moth collected in 
the city of Lynn, some 7 miles from the colony site. This would 
indicate a rapidity of dispersion in excess of that of Compsilura, 
and one which is distinctly satisfactory. 
Another specimen was reared in the fall of 1910 from a caterpillar 
of the fall webworm collected in the open, and this was also con- 
sidered as satisfactory evidence of its ability to exist here. At the 
present time there seems to be every reason to expect that it will be 
found in 1911 over a more considerable territory and in a much 
greater abundance than in 1910. 
ZYGOBOTHRIA NIDICOLA TOWNS. 
The few caterpillars which Mr. Titus saved from among those 
emerging from the hibernating nests in the spring of 1906 all died 
before pupation, and no other parasite than Apanteles and a single 
specimen of the Apanteles parasite, Mesochorus pallipes, was reared 
from them. In 1907 trouble was again experienced in carrying the 
caterpillars from imported nests through to maturity, but among the 
thousands which were fed in the cages at the North Saugus laboratory, 
as described in the account of the introduction of Apanteles, a few did 
95677°—Bull. 91—11——19 7 
