200 



PAEASITES OF GIPSY AND BROWN-TAIL MOTHS. 



List of secondary parasites reared from American cocoons of Apanteles in the order of relative 



abundance. 



[In this list the number of individuals of Apanteles killed, not the gross number of the secondaries reared, 

 is given. In case of tie, the species which was relatively the more important in the particular lot or lots 

 from which it was reared is given preference.] 



Hypopteromalus 1, 276 



Dibrachys 583 



Asecodes 



Hemiteles No. 60 



Hemiteles No. 61 



Hemiteles No. 75 



Pezomachus 



Eulophid 



Hemiteles No. 62 



161 



2 58 

 52 



2 49 

 64 

 71 

 18 



Pezomachus No. 65. 

 Pteromalid No. 68 . 

 Hemiteles No. 63... 

 Pteromalid No. 70.. 



Eupelmus 



Hemiteles No. 66... 

 Anastatus 



15 

 6 

 5 

 2 

 2 

 2 

 1 



Total 2,288 



Local conditions as affecting the control of this parasite through hyperparasites 

 were well represented in 1909 by a comparison between the relative abundance of sec- 

 ondary parasites in cocoons from two colonies, the " Reading- Wilmington, " and the 

 '' West Manchester, " which were planted at about the same time. In both repro- 

 duction was abundant, and a large number of cocoons was collected from each. Only 

 those which were left in the field until all of the Apanteles which remained healthy 

 had issued are counted in the following: 





Reading-Wilming- 

 ton colony. 



West Manchester 

 colony. 





Cocoons. 



Per cent. 



Cocoons. 



Per cent. 



Apanteles 



70 

 624 



8 

 218 



8 

 68 



1 

 23 



543 

 162 

 22 

 89 



66.5 



Hyperparasites 



20 



Predators 



2.5 



Unhatched Oct. 20 



11 



Total 



920 





816 











The West Manchester colony was located in rather dense forest, with a swamp, 

 partly overgrown with brush and partly with thick forest on one side. The trees 

 were large, and cocoon masses were frequently far beyond reach. Only those which 

 could be reached from the ground were collected. There were more cocoons in this 

 colony than in the other, but they were not quite so easily collected. It is of course 

 possible that the larger number of cocoons explains in part the smaller percentage of 

 hyperparasitism . 



The increase in hyperparasitism in the cocoons of the second generation over the 

 first can only be demonstrated in the case of the West Manchester colony, which was 

 the only one where there was a second generation in sufficient abundance to permit 

 of adequate field collections. In this it is or appears to be very striking, when 

 the fact is taken into consideration that a considerable number of parasites hibernated 

 in the cocoons of the second, while none were found in those of the first which failed 

 to hatch after the 1st of September. 



1 Many Asecodes remaining unhatched within the cocoons will doubtless attempt to hibernate. 



2 Hemiteles No. 60 and Hemiteles No. 75 may possibly be one and the same species. It is possible, too, 

 that further study will cause a change in the relative position of the two species. 



