GYPSY AND BROWN-TAIL MOTHS. 37 



larly in 1909, new colonies have been located in various parts 

 of eastern Massachusetts. There is no better method for the 

 recovery of the parasite from the field than the collection of 

 gypsy or brown-tail caterpillars and their confinement in cages, 

 where they can be fed, and where the parasite can be secured 

 in case it is present and emerges. This is a tedious process, in- 

 volves a large amount of labor, and in the case of the brown-tail 

 caterpillars entails much discomfort in its execution; and at- 

 tempts to determine the distribution of the parasite in the field 

 have not been as thorough as it is intended that they shall be 

 in 1910. Nevertheless, it was recovered from the field upon 

 several occasions in the course of the summer of 1909, and there 

 seems not to be any question that it is thoroughly established 

 and widely distributed in Massachusetts at the present time. 

 Its rate of increase, if the widespread distribution is taken into 

 account, is wholly satisfactory, and, as indicated by the field 

 collections, is as great as of Calosoma and perhaps as of Mono- 

 dontomerus. It must be remembered, in this connection, that 

 there is no simple means of determining its distribution, as is 

 the case with both of the other species mentioned ; and further- 

 more, that, although it was liberated in 1906, it was not until 

 so late in the season as to make a generation upon the gypsy 

 or brown-tail caterpillars improbable during that year. It was 

 not until 1907 that it can be considered as having had its first 

 good opportunity for reproduction in America, and the fact 

 that it was found to be generally distributed the third season 

 in the field is indicative of a particularly satisfactory progress. 

 It is not a very important parasite of either the gypsy or the 

 brown-tail moth in Europe. It has never been received from 

 Japan, and it is not expected that it will become of more than 

 relatively minor importance in either connection here, as com- 

 pared with Blepharipa and Glyptapanteles. At the same time, 

 it has points in its favor not possessed by any other parasite, 

 notably, its ability to pass one generation upon the brown-tail 

 caterpillars and another immediately after upon those of the 

 gypsy; and it is likely to gain in effectiveness, in this manner, 

 a part of what it loses through its probable inability to com- 

 plete its seasonal cycle without the assistance of an alternate 

 native host. It is very democratic in its choice of hosts, and 



