NARRATIVE OF PROGRESS OF WORK. 61 
on the northwest, and from the Pyrenees on the southwest to the 
shores of the Baltic on the northeast. In spite of the voluntary 
assistance of such men as Rene Oberthiir and Josef Jablonowski, the 
expense of getting these nests to Boston had been very considerable, 
and the moment when this examination was begun was considered 
to be rather a critical one. No published record of the rearing of 
parasites from these winter nests was recalled by the senior author 
or by any of his European correspondents, and the expensive experi- 
ment rested solely on the unpublished observation of Jablonowski, 
and he himself had-simply seen parasites emerge from nests in the 
spring. Would they prove useless? Had the parasitic insects, even 
if useful, simply crawled into the nests for hibernation? Or were they, 
some of them, true parasites of the young larve? Representative nests 
were examined from a number of different localities, and the relief 
and joy were great when parasitic larve were found in considerable 
numbers in each of the nests examined, feeding within the nest pockets 
externally upon the brown-tail larve. This particular experiment 
was a success, and the expenditure of money and trouble was justified. 
About April 25 these parasites began to issue from the nests. The 
nests had been gathered in all from 33 different localities, and from 
some of them only a small number of parasites was reared. In all, 
about 70,000 issued, of which about 8 per cent were hyperparasites. 
In the rearing cages above mentioned it was a comparatively easy 
matter for Mr. Titus to separate the hyperparasites from the true 
parasites and to destroy the former. Of the species issuing in that 
spring—and they continued to issue until about June 15—there were 
two species which appeared to be important, namely Pteromalus 
egregius Forst. and Habrobracon brevicornis Wesm. The latter species 
proved later to have entered the nests for hibernation only. 
With the cooperation of Mr. Kirkland, several localities were found 
in which there was slight danger of forest fire and in which no work 
against the moths would apparently be undertaken for at least some 
months to come, and colonies of various sizes—the three principal 
ones including, respectively, 10,000, 15,000, and 25,000 parasites— 
were liberated in the open. Outdoor cages had been built over trees, 
and some smailer colonies of the parasites were placed in these cages. 
Both the outdoor experiments and the open experiments were 
seriously hampered, however, by the fact that the season proved to 
be one of extraordinary humidity, which caused the appearance of a 
fungous disease which destroyed a large proportion of the brown-tail 
moth larve in the vicinity of Boston. 
Coincident with the issuing of these parasites from the nests, as the 
season grew warm the young larve swarmed from the nests and 
filled the glass tubes in the breeding cages and were constantly being 
destroyed by the assistants in the laboratory, and when the parasites 
