GYPSY AND BROWN-TAIL MOTHS. 27 



stages in the reproduction cages is 2,000,000. It is by no means 

 sure that the species will go through tlje winter in the open as 

 successfully as is hoped will be the case ; but no obstacle threat- 

 ens to prevent the liberation of several millions of the parasite 

 during the summer of 1910. 



The reproduction of the parasite in the field, as a result of 

 the earlier attempts at colonization, has been far in excess of 

 expectations. The rate of reproduction in the laboratory, which 

 averages only about ten-fold each generation, was greatly ex- 

 ceeded, and hundreds of thousands of eggs were knovm to be 

 parasitized in the immediate vicinity of the colony sites. In 

 the one colony which has been most carefully watcher^ ^^-^ iDara- 

 sitized eggs (Fig. 6) average some 30 to the mass everywhere 

 within a radius of 50 yards, and the masses in a few places are 

 so thick as to hide the bark on the trees. Beyond 50 yards the 

 numbers fall off very rapidly; but the species has been found 

 several hundred yards from the point of liberation, in striking 

 contrast to Anastatus, which traveled only 100 feet. 



It is hoped that a strong colony will be established in every 

 tovTn in the infested district during the coming summer ; and if 

 the same rate of dispersion indicated during the past fall con- 

 tinues, and the parasite demonstrates its ability to exist under 

 American conditions during the entire year, it should be gen- 

 erally established throughout the infested area in two or three 

 years more. 



It must not be forgotten, however, that it has not yet proven 

 itself adaptable to American conditions at all seasons. Like the 

 other egg parasite, Anastatus, the only known host is the gypsy 

 moth; but, unlike that species, its life is not correlated to that 

 of its host. It is not known how it passes the winter, and, al- 

 though living adults issue within a few days from egg masses 

 brought in from the vicinity of the colonies in December, it is 

 possible that they will not survive the cold weather which is 

 bound to follow in January and February.^ There is also a 

 possibility that in Japan there is some other lort of egg subject 

 to its attack, in which it passes a generation during the early 



* This statement was written in December. It has since been found that all of the larvffi and 

 pups of the parasites perished during the cold weather in January, but that adult parasites, of 

 which there are known to be many in the field, lived through it. Whether they will survive 

 the remainder of the winter is yet to be demonstrated. 



