118 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



There is very little published information at hand bearing upon 

 this subject, and that which is available is general rather than defi- 

 nite in its tenor. Anyone who for the first time encounters a tree 

 covered with caterpillars of the gipsy moth dead and dying through 

 the effects of the "wilt" disease is very apt to think that at last 

 the gipsy moth has met its Waterloo, and disillusionment has only 

 come in the present work as the result of several years' consecutive 

 observations in the same or similar localities. In like manner the 

 observations of foreign entomologists, or of American entomologists 

 traveling abroad, as to the actual effectiveness of the parasites in 

 accomplishing the control of the moth have to be taken with a grain 

 of conservatism. Parasitism by a species as conspicuous as Apan- 

 teles Julvipes to the extent of 50 per cent would undoubtedly create 

 a most favorable impression and the more conspicuous parasitized 

 caterpillars would easily appear to outnumber the healthy. This 

 amount of parasitism would certainly be inefficient in America unless 

 it were supplemented by a much larger amount of parasitism by 

 other species. 



On this account it has been necessary to depend very largely upon 

 the study of the parasite material imported from abroad as a source 

 for information of this sort. From the beginning accurate notes 

 have been kept of the many thousands of boxes of eggs, caterpillars, 

 and pupae of the gipsy moth and brown-tail moth, in which are 

 recorded the locality from which each lot came, its condition on 

 receipt, and the number and variety of parasites reared in each 

 instance. The records are necessarily based in most instances upon 

 such information as may be gained through a study of the condition 

 of the material on receipt and the parasites reared, but in a few 

 careful dissection work has been carried on to determine the true 

 conditions, and thus to check up the results of the rearing work. 

 It has been found that the amount of dependence which can be 

 placed upon the rearing records is relatively small, and that noth- 

 ing more than a general idea of conditions actually prevailing can be 

 gleaned from them. Nearly always some of the caterpillars or pupse 

 are dead or dying upon receipt as a result of the ordeal through which 

 they have passed. On the average, taking the gipsy-moth material 

 from all localities, not more than 25 per cent has arrived in good 

 condition (when the shipment of eggs is excepted). The brown- 

 tail moth material has averaged very much better, and probably 75 

 per cent has been in good condition on receipt. 



It has been found that sometimes a larger percentage of parasites 

 than of caterpillars or pupae died en route, while at other times these 

 conditions are entirely reversed, and since dissections can not be 

 made in every instance, it has been necessary to consider the para- 

 sitism indicated by the notes upon two different bases, i. e., that of 



