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 si 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 pupe of the moth in America, which have not been 
studied sufficiently well as vet. 
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 Brullé. The true JT. melano- 
cephala appears not to have been reared from this host. The import- 
ance of TJ. 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 (Mala- 
cosoma disstria Hiibn.) 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 pup 
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 pup 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 
