PARASITISM OF (ilPSV 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 pupflB of the moth in America, which have not been 
studied sufficiently well a s yet. 
The following Dative parasites have been reared from the gipsy 
moth in Massachusetts: 
Tm KRONIA Fl'I.VESCENN CRESS. 
This, the most common American parasite completing its trans- 
formations up<m the gipsy moth, was mentioned by Forbush and 
Bernald in I heir comprehensive report upon u The ( typsy Moth 99 under 
the name of 77" inn m melanocephala Brulle*. The true T. mtlano- 
C( j>liahi appeals not to have been reared from this host. The import- 
ance of '/'. (ill r< set lis as a gipsy-moth parasite is indicated by the 
summarized results of the rearing work conducted in 1910. 
Tn his account of the parasites of the forest tent caterpillar {Mahi- 
cosnmd ilisstrid Iliibn.) in New Hampshire by the junior author it was 
credited a- being ;i secondary parasite of I'm, pin coiMjitisitor 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 he a true primary parasite, but one 
which, [ike Pimpla conguisiicr itself, is able to complete its transfor- 
mation, under a variety of circumstances. The supposed secondary 
parasitism, in this instance, is to be classified lather 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 pupse 
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 pupa? of the gip>y 
moth collected in the held, but it is of extremely rare occurrence as a 
parasite of this host, so far as recent rearing work indicates. It was 
