APANTELES MELANOSCELUS GIPSY-MOTH PARASITE. 23 



SECONDARY PARASITISM. 



Cocoons of the first generation are not seriously attacked by sec- 

 ondary insects. Small collections of cocoons of this generation are 

 made each year over a considerable area and rarely are they para- 

 sitized over 10 per cent ; more often not more than 2 or 3 per cent are 

 killed by secondaries. 



Unfortunately it is a different story with the hibernating brood, 

 for approximately 75 per cent are killed annually by native secondary 

 insects and ants. This seriously handicaps the increase of A. melan- 

 oscelus. Among the insects which have been reared from the hibernat- 

 ing cocoons are at least three Ichneumonidae, and members of the 

 Pteromalidae, Elasmidae, Eurytomidae, Entedontidae, and Eupel- 

 midae. In this complex there are secondary, tertiary, and possibly 

 quaternary and quinquenary insects. An investigation of the life 

 histories and host relationships of these insects has received consid- 

 erable attention at the laboratory, but has not been completed. Some 

 of these insects have several generations during the early fall and 

 then hibernate within the cocoons of A. Tnelanoscelus. 



THE VALUE OF A. MELANOSCELUS AS A GIPSY MOTH PARASITE. 



The problem of obtaining the actual percentage of parasitism of 

 the gipsy moth by A. melanoscelus or by any of the other introduced 

 parasites, except the egg parasites, is a difficult and complicated mat- 

 ter involving many factors. Records at the Gipsy Moth Laboratory 

 show that larvse picked promiscuously from tree trunks and foliage 

 to-day may give 30 per cent parasitism, while to-morrow the same 

 number of larvse, collected by the same individual, in the same man- 

 ner, and in the same locality, may npt even show the presence of the 

 parasite. 



For a number of years collections of gipsy-moth larvse have been 

 made daily through the entire larval period at Melrose and Stone- 

 ham, in an attempt to learn the true status of the parasites in that 

 section. Each collection contained 100 larvse all of the same stage. 

 The collections of each stage were continued as long as that particular 

 stage could be found, and collections of the next stage were started 

 as soon as 100 larvse of the next stage could be found. As there is 

 quite an overlapping of stages, there were very often two collections 

 on the same date at the same place. All of the collections were kept 

 separate and the larvse were fed in trays until all of the parasites 

 had issued. The trays were examined each day and any parasites 

 which issued were removed and recorded. Individual collections, con- 

 taining 100 caterpillars each, gave from nothing to as high as 40 

 per cent parasitism of second-stage gipsy-moth larvse for the spring 



