December, '09] JOURNAL of economic entomology: 453 



The Primary Parasites 



The list of primary parasites which were reared or otherwise 

 secured from the several hosts is included in the following table, 

 together with the numbers, gross and proportionate from each : 



The most surprising feature of this list is the very considerable 

 percentage of parasitism of cecropia by Tachinid flies, amounting to 

 nearly three times the total parasitism by Hymenoptera. There are 

 at least two species, the larv^ of one of which pierce the cocoon of 

 the host and drop to the ground for pupation, leaving as characteristic 

 evidence of their occupancy the exit hole in the cocoon, the first and 

 second stage moult skins within the host remains, and frequently, but 

 by no means always a few dead maggots which were too weak to ac- 

 company their healthier companions. None of these signs are con- 

 spicuous, and all might be overlooked in a casual study of the cocoons, 

 and it is easily possible that a portion of those studied by Dr. Smith 

 may have been parasitized by the same or another species with similar 

 habits. 



No adults of any species having this habit were reared. An exam- 

 ination of the larvte which were left behind makes it probable that 

 they were all of one species, and possibly that they are to be referred 

 to the genus Tachina, as they possess very many of the characters of 

 Tachitia mella WaUv. 



The other species which is about equally abundant pupates within 

 the cocoons, and has been determined as Achaetoneura frenchii W. 

 Not all of the puparia hatched, but from the 44 cocoons a total of 550 

 flies, an average of between 12 and 13 from each, were reared. If it 

 had been present in the New Jersey or Long Island material it would 

 most certainly have been observed, and its absence is worthy of com- 

 ment. 



The average number of flies issuing from one cocoon is no indication 



of the number which may sometimes mature on one host. In one 



instance Mr. Townsend counted no less than 90 puparia from 



which the flies had emerged and in another he found and counted 



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