EGG PAKASITES OF THE BROWN-TAIL MOTH. 259 



A large number of parasitized eggs, containing the brood in various 

 stages of development, were placed in cold storage and kept until 

 the following June and July, when, upon being removed, a few of 

 the parasites completed their transformations. With these as pa- 

 rents large numbers were reared in the laboratory upon the fresh 

 eggs of the brown-tail moth, at that time abundantly available, and 

 the cold-storage experiment was repeated during the winter of 1908-9 

 with much better results than before. An abundant supply of parent 

 females was available in the summer of 1909, and a great many 

 thousands of the parasite were reared and liberated under the most 

 favorable conditions which could possibly be desired or devised. 

 Many thousands were known to have issued from parasitized eggs 

 contained in small receptacles attached to the branches of the trees 

 upon which the brown-tail moths were even then depositing eggs 

 in abundance. 



No false hopes were felt as to the probable success of this venture. 

 It has been amply demonstrated in the laboratory that the females 

 were unable to penetrate the egg mass for the purpose of oviposition, 

 and the location in the mass of the few eggs parasitized by the 

 American race of pretiosa indicated sufficiently well the inability of 

 that species to do better in the open than either it or the European 

 would do in confinement. 



Accordingly no disappointment was felt, when it was found that 

 the degree of parasitism effected by the European species in the 

 immediate vicinity of the colony sites was hardly, if any, greater than 

 that ordinarily effected by the native species. It is hardly a physical 

 possibility for Trichogramma to effect more than a small percentage 

 of parasitism in the egg mass of the brown-tail moth, and the value 

 of the genus as represented by the three species or forms which have 

 been studied at the laboratory is slight. 



At the same time, it is not felt that the labor which has been 

 expended in an attempt to give Trichogramma a fair test has been 

 altogether lost. There are numerous other hosts upon which it is 

 a very efficient parasite, and it is easily conceivable that at some 

 future time it will be found possible to utilize it in some manner 

 which the circumstances themselves will suggest. 



As a possible example may be mentioned the tortricid Archips 

 rosaceana Harris, which at times becomes a pest in greenhouses 

 devoted to the growing of roses. In Volume II, No. 6, of the Journal 

 of Economic Entomology, Prof. E. D. Sanderson describes such an 

 outbreak in a large rose house in New Hampshire under the heading 

 of " Parasites." Prof. Sanderson says: 



The outbreak observed by us furnished a case of the most complete parasitism we 

 have ever seen. When first observed, in late July, from one-third to one-half of the 

 eggs were parasitized by a species of Trichogramma. Two weeks later it was difficult 



