U. S. D. A., B. E. Tech. Ser. 19, Pt. Ill, Issued March 22, 1911. 



TECHNICAL RESULTS FROM THE GIPSY MOTH PARASITE LABORATORY. 



111. Investigations into tlie Habits of Certain Sarcopliagidae. 



By T. L. Patterson, 

 Assistant in Biology, Sheffield Scientific School, Yale University. 



INTRODUCTION.' 



That there are among the Sarcophagida3 a number of species which, 

 to all intents and purposes, are primary parasites of grasshoppers is a 

 fact concerning which there is no ground left for argument. Whether 

 the young larvae of these flies bear a relation to the living host which 

 is in any way comparable to the extraordinary intimacy which char- 

 acterizes the relations between the tachinid parasites and their hosts 

 is beside the present question. They assuredly do gain access to the 

 living body of their host, and after a time destroy it, and by so doing 

 qualify themselves to be considered among the insect parasites. 



There are numerous species of the Sarcopliagidae which have been 

 reared in association with the gipsy moth {Porthetria dispar L.). 

 Each year after the caterpillars have pupated and when the moths 

 are beginning to emerge, interested persons have found pupae with 

 the shell apparently unbroken, the contents in a state of decomposi- 

 tion, and an active sarcophagid larva luxuriating in the surroundings 

 thus provided. The condition of the pupa containing the sarcopha- 

 gid is always different from that of a pupa containing a tachinid 

 maggot, but the distinction is not instantly apparent nor easily 

 described. To the ordinary observer the pupa containing the sar- 

 cophagid answers perfectly to the description of a pupa destroyed 

 by a tachinid, and each year it has been necessary to explain anew 

 the difference between parasite and scavenger. That sarcophagid 

 maggots found under these conditions are always scavengers and 

 never parasites has never seriously been questioned. 



It must be admitted, however, that in thus rather summarily con- 

 signing the whole group of sarcophagids to the role of scavengers, in 

 so far as their relations to the gipsy moth were concerned, there has 

 been an undercurrent of uneasiness lest among them should eventu- 



1 Introduction by W. F. Fiske, in charge of Gipsy Moth Parasite Laboratory, P.ureau of 

 Entomology, Melrose Highlands, Mass. 



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