PARASITES HIBERNATING IN BROWN-TAIL WEBS. 273 
in the matter of preventing the escape of the caterpillars, but aside 
from that, the experiment promised to be highly successful. Instead 
of losing track of the parasites immediately following their liberation, 
they were found to be present in abundance in and about these cages 
throughout May and June, and even in July Mr. Mosher (who con- 
ducted this work) observed a few alive and apparently waiting until 
the next generation of hibernating caterpillars would be open to their 
attack. 
Not all of the Pteromalus brood was liberated in this manner, but 
a part of the artificially infested nests was placed in cold storage at 
a constant temperature of approximately 30° F. and kept during the 
summer and until the formation of the brown-tail moth nests in the 
fall. Then a part of them was removed as a check on the condition 
of the remainder, and when it was certain that many, if not most of 
the Pteromalus had survived, a considerable number of them was 
allowed to issue in the open in a locality where they would find an 
abundance of fresh nests of the brown-tail moth ready at hand. 
Others of the stored Pteromalus were held for the purposes of winter 
reproduction, in case the further colonization of the parasite seemed 
worth attempting. 
At first it appeared that the colonies of 1908, both spring and fall, 
were successful. In the vicinity of each of them (but particularly of 
that which was planted in the fall) the larve of the parasite were 
found in the nests of the brown-tail moth, and for the first time it 
was known to have lived over summer out of doors. Extensive rearing 
work was organized in the laboratory, with the intention of securing 
at least 1,000,000 for colonization in 1909, and certain technical inves- 
tigations into the life of the parasite, which were begun in the spring 
of 1908, were continued. 
The results of these biological investigations soon became startling 
in their nature. Gradually, as they were continued, and the results 
of one experiment after another became apparent, a tale of insect 
duplicity was unfolded the like of which has never been quite equaled 
in any similar investigation. It is not possible to give the story in 
anything like complete detail, but a brief summary ought to be pre- 
sented, if for no other purpose than to illustrate the degradation to 
which a parasite may sink. 
It was found that the instinct of the female Pteromalus was first 
to seek the immediate vicinity of the feeding caterpillars, or of the 
nests or molting webs which they had deserted, and second to ovi- 
posit upon nearly anything which she encountered, providing it 
resembled in the slightest degree a dormant caterpillar of the brown- 
tail moth inclosed in its hibernating web (fig. 66). Attempted 
Oviposition upon active caterpillars was only one of innumerable 
 95677°—Bull. 911118 
