go JOURNAL OB" ECONOMIC ENTOMOLOGY [Vol. 3 



parent females are both attracted to the primary host primarily for 

 its own sake. In hyperparasitism one of them is attracted to the 

 primary host secondarily and incidentally, and for the sake of the 

 primary parasite which it harbors. 



It is difficult to draw a hard and fast line which shall separate all 

 forms of double parasitism into either the one or the other. There are 

 several instances in which it is difficult to determine which relation 

 the parasite actually occupies. Theronia, for example, is indubitably 

 primary on occasion, but at the same time so frequently superparasitic 

 as to make it appear that it is attracted by the presence of the other 

 parasite as strongly as by the primary host. It has been the cause of 

 a great deal of perplexity in the work of parasite introduction, solely 

 on account of this doubt as to its true nature, and it was a long time 

 before it was definitely determined to be primary more frequently 

 than it appeared to be secondary. It is at present considered to be a 

 true primary parasite, but one which is in danger of becoming a true 

 hyperparasite in the course of its further evolution. 



Manifestations. The manifestations of superparasitism are exceed- 

 ingly diverse, and as in the case of Theronia oftentimes puzzling to 

 the observer. The most conspicuous is that which has been defined 

 by Mr. W. D. Pierce in his discussion of the parasites of the cotton 

 boll weeviP as "accidental secondary parasitism," a term which 

 applies very well indeed to this form of superparasitism, but not at 

 all to the others. Accidental secondary parasitism occurs frequently 

 in connection with other hosts than that upon which Mr. Pierce con- 

 ducted his investigations, and it is characterized by the larva of one 

 parasite developing at the expense of another in very much the same 

 manner as would that of a true secondary parasite under similar con- 

 ditions. The only real difference is that already set forth in the 

 definition given, that in the one case the second parasite is attracted 

 to -the primary host, and in the other to the host because it is already 

 parasitized. 



In the very great majority of instances one parasite is destroyed 

 through the premature death of the primary host due to the attack of 

 the other. Under such circumstances the evidences of superparasitism 

 are only apparent through a careful dissection and microscopic exam- 

 ination of the host remains. The larva of the parasite which suffers 

 destruction may or may not be devoured by the other in such instances. 



Frequently both parasites die without either completing its trans- 

 formations, but usually, though not always, they are stunted and weak- 

 ened, and their powers of reproduction are seriously curtailed. Sev- 



-BuU. United States Department of Agriculture, Bureau of Entomology. 



