238 PARASITES OF GIPSY AND BROWN -TAIL MOTHS. 
have done so had the cocoons of the native not been associated with 
the proper host of the other. 
The third species, Pimpla hrassicarise Poda, is much less commonly 
reared from either the gipsy moth or the brown-tail moth than the 
other two. Apparently its habits are identical. 
Hardly enough have been received of the three Japanese species to 
indicate their relative abundance. The most striking of them, 
Pimpla pluto, appears to be the only one of the trio which has been 
described, and to the others Mr. Viereck has given the names P. 
disparis and P. porthetrix. It is possible that they are just a trifle 
more common in connection with the gipsy moth in Japan than are 
the corresponding species in either Europe or America. At the 
same time Theronia has outnumbered all three together in the 
Japanese material studied at the laboratory. 
Hardly anything is known about them. Not enough have been 
received to make colonization possible, and only upon one occasion 
to permit of laboratory reproduction with fertilized females, and upon 
this occasion there was no time to devote to their further study. 
Presumably, except for minor differences, all of the Japanese 
Pimpla will be found to conform very exactly in biology and habit 
to the American and European. All will probably be found to 
attack a very large variety of hosts, and all will defer their attack 
until their host has entered the prepupal or pupal state. The 
females of all will probably be ready to oviposit for a new generation 
almost immediately following their emergence, and the length of life 
cycle, dependent upon temperature, will be about three or four weeks. 
There will necessarily be more than one generation each year unless 
the hibernating individuals should live long enough to deposit eggs 
for another hibernating generation, as might easily be possible in the 
case of Pimpla instigator, and conceivably possible in the case of 
each of the others. 
Pimpla conquisitor and Pimpla pedalis are among the most 
generally effective of the pupal parasites of the medium-sized cocoon- 
spinning Lepidoptera in the Northeastern States. The first named 
is perhaps the most common and effective of all the parasites of the 
tent caterpillar and about as effective as any other one as a parasite 
of the tussock moth. It does not vary much in relative abundance 
from one year to the next, and appears to play a part which is rather 
to be compared to that taken by the birds than to that taken by 
most of the parasites. It is, like Theronia, so impartial in its atten- 
tions to all of the different species of its hosts as scarcely to be 
affected by an unusual abundance or unusual scarcity of any one 
among them in particular. 
The same is very likely to be true of the European and Japanese 
species. The part played by each in the localities where it is native 
