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 tins 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 



