GYPSY AND BROWN-TAIL MOTHS. 15 



while it has been recognized as one applicable in many instances, 

 has been established much more firmly than ever before, as a 

 result of the work which has been done at the laboratory. It 

 would be impossible to speak with so much assurance had it not 

 been for a series of investigations upon the parasites of several 

 native insects, similar in certain important respects to the gypsy 

 moth. These investigations have seemed sometimes to be out- 

 side of the main point at issue ; but their value in establishing, 

 as they have, this and certain other general propositions, has 

 justified many times over the relatively small expenditure nec- 

 essary to carry them on. 



PARASITES OF THE GYPSY MOTH IN JAPAN. 

 The Japanese race of the gypsy moth is larger and stronger 

 and in certain other respects different from that found in Eu- 

 rope or in America. One important characteristic is its greater 

 fecundity, the number of eggs in a mass being from one-fourth 

 to one-third greater, on an average, than in the egg mass of the 

 typical European variety. This is indicative of greater powers 

 of resistance to natural controlling factors, and, conversely, of 

 the existence of more effective controlling agencies in Japan 

 than in Europe. It is very significant that it is not at all an 

 important pest in Japan, and that, in the opinion of the native 

 entomologists and of every American entomologist or other- 

 wise trained observer who has had opportunity to acquire first- 

 hand information, the parasites are very effective in its control. 

 Thirteen species of primary parasites have been reared from 

 eggs, caterpillars or pupae of the gypsy moth from Japan, but 

 only 7 of these can be considered as of importance in bringing 

 about its control. The others have been consistently rare, and 

 some of them have never been recorded as parasites by the Japa- 

 nese themselves. 



These parasites, in every instance but one, are either identical 

 in all respects, or, if not absolutely the same, exceedingly similar 

 to the parasites in Europe. It is unfortunately necessary to 

 refer to them by their technical names, since none of them have 

 been considered as of general interest hitherto, and other than 

 such names there are none. They are listed in Table 1. 



