PARASITISM OF GIPSY MOTH IN AMERICA. 137 



serious attempt to determine whether this actually happens in the 

 field has been made, but undoubtedly it does occasionally result when 

 the parasite larva finds itself under unnatural surroundings. It is 

 thus well within the bounds of possibility that effective parasitism 

 should pass unnoticed in the course of investigations in which reliance 

 is placed entirely upon the results of rearing work. 



As will be shown in another place, death of the host through super- 

 parasitism by a species fitted to attack it may similarly* occur without 

 the true cause becoming apparent. 



A sufficiently large quantity of the native caterpillars of the gipsy 

 moth has been dissected at the laboratory to indicate that such con- 

 cealed parasitism, if it is ever a factor in the control of this insect, 

 is of rare occurrence, or else of insignificant proportions. This can 

 not be said of the pupae of the moth in America, which have not been 

 studied sufficiently well as yet. 



The following native parasites have been reared from the gipsy 

 moth in Massachusetts: 



Theronia fulvescens Cress. 



This, the most common American parasite completing its trans- 

 formations upon the gipsy moth, was mentioned by Forbush and 

 Fernald in their comprehensive report upon " The Gypsy Moth" under 

 the name of Theronia melanocephala Brulle. The true T. melano- 

 cephala appears not to have been reared from this host. The import- 

 ance of T. fulvescens as a gipsy-moth parasite is indicated by the 

 summarized results of the rearing work conducted in 1910. 



In his account of the parasites of the forest tent caterpillar (Malar- 

 cosoma disstria Hubn.) in New Hampshire by the junior author it was 

 credited as being a secondary parasite of Pimpla conquisitor Say, 

 and was not recognized as a primary parasite. Investigations at the 

 laboratory have served to throw considerable light upon its life and 

 habits, and it is now known to be a true primary parasite, but one 

 which, like Pimpla conquisitor itself, is able to complete its transfor- 

 mations under a variety of circumstances. The supposed secondary 

 parasitism, in this instance, is to be classified rather as "superpara- 

 sitism" and is believed to result through the circumstance that the 

 primary host chances to contain the larva of Pimpla, rather than 

 through the deliberate searching out by the parent Theronia of pupae 

 thus parasitized. In its relations to the gipsy moth, which is not 

 successfully attacked by Pimpla at all frequently, Theronia has 

 always been a primary parasite so far as known. 



Pimpla pedalis Cress. 



One or two specimens have been reared from the pupae of the gipsy 

 moth collected in the field, but it is of extremely rare occurrence as a 

 parasite of this host, so far as recent rearing work indicates. It was 



