AMOUNT OF CONTROL NEEDED FOR GIPSY MOTH. 115 
the actual work of importation was going to be considerably more 
than had been expected two years before and that practical results 
could not possibly be achieved until long after the time originally 
predicted. Additional information upon the biology and habits of 
each of the several parasites, if not necessary in every instance, was 
necessary in some and desirable in all, and here again additional 
expenditures became imperative. Furthermore, the situation was 
such as to make of very doubtful advisability the indiscriminate 
importation of very large quantities of parasite material before a 
better knowledge of the parasites themselves had been secured. The 
repetition of the very large shipment of brown-tail hibernating nests 
winter after winter, as will be described in another chapter, is an 
instance in point. _Had we been in possession of a complete knowl- 
edge of the parasites hibernating in those webs at the beginning, per- 
haps one winter’s importation would have been sufficient. 
There was no certainty that the results of the technical studies as 
conducted at the American laboratory would be sufficiently full and 
complete to answer our purposes and make possible the intelligent 
continuation of the work. Should we fail in this respect, the only 
alternative to a discontinuation of the introduction work in advance 
of its logical conclusion was the establishment of a laboratory abroad, 
at a considerable expenditure. 
With these several reflections, it was inevitable that the advisability 
of continuing the work beyond the time limit originally set should 
come into question. Accordingly, in anticipation of the necessity for 
making a decision when the time for it should arrive, the whole 
proposition was subjected anew to the closest sort of scrutiny from 
every point of view. 
The successful consummation of the work involved, first of all, the 
establishment in America of a group of parasites or other natural 
enemies sufficiently powerful to meet and offset the prevailing rate of 
increase of the gipsy moth. This, as determined by Forbush and 
Fernald, was at least sixfold annually; as determined by actual 
observation in the field, it was often far in excess of sixfold. 
Before the continuation of the work could be recommended it was 
absolutely necessary to arrive, first, at some conclusion as to the 
amount of parasitism (gauged on the percentage basis) which would 
be required in order to offset this increase and maintain the gipsy 
moth at an innocuous minimum; and, second, whether parasitism 
to such an extent actually prevailed abroad or whether natural con- 
trol in those localities where it was obviously effected was due to the 
increased efficiency of other agencies. 
In so far as the first proposition was concerned, it was obvious from 
the beginning that if enough egg masses could be destroyed each fall 
so that the number remaining would be no greater than that which had 
