12 IMPORTED PARASITES. 



capped through the practical necessity of entrusting the actual 

 work of collection and shipment in foreign countries to others 

 than those most familiar with the nature and needs of the various 

 parasites. The several trips which Dr. Howard has made 

 abroad, wholly or in part in the interest of this undertaking, has 

 enabled him to meet the foreign agents, and to enter into ex- 

 planations which were infinitely more satisfactory than any 

 which could be effected through correspondence. At the same 

 time, it has been impossible to convey to these agents the detailed 

 information which would enable them to work to the best advan- 

 tage, nor would it be possible for them to acquire this in any 

 manner short of actual experience in the laboratory. In par- 

 ticular has it been handicapped by the very short period during 

 which work upon any particular parasite could be carried on in 

 any one year. Parasites of the pupa, or of certain stages of the 

 caterpillars, could be collected in Europe or Japan only during 

 the season when pupae or caterpillars in those particular stages 

 occurred in the open in those countries ; and the aggregate period 

 during which it has been possible to work with some parasites 

 in the five years since the inception of the work does not exceed 

 as many months. 



In all, there have been received at the laboratory in a living 

 condition between 40 and 50 species of parasites of the brown- 

 tail moth and of the gypsy moth. Of these, about 30 attack the 

 gypsy moth, but only about two-thirds of that number can be 

 considered as at all important. The others seem always to be 

 rare in the countries to which they are native, and never to be- 

 come so abundant as to affect the increase of the moth. No 

 parasite, however rare it might seem to be, has been ignored, 

 once it was demonstrated to be a primary upon the gypsy or the 

 brown-tail. A great deal of time has been spent in attempting 

 to discover the probable reason for apparent inconsequence in so 

 many instances ; and a great deal of work has been done to dem- 

 onstrate that this was due to other causes than defective methods 

 in the collection and subsequent handling of the parasite im- 

 portations. 



One by one, as material has been imported under different 

 conditions and from different coimtries, different species of 

 parasites have been added to the list, until it has exceeded in 



