No. 637] 



PARASITISM 



141 



independent origin, and hence of no classificatory im- 

 portance. 



Comparative anatomy and post-embrj'onic develop- 

 ment show very clearly that, with the exception of some 

 secondarily phytophagous forms, only the primitive 

 Hymenoptera are phytophagous. As one can not seri- 

 ously question the monophyletic origin of the order, the 

 varied food-habits now represented must have been de- 

 rived from some form of vegetarianism. 



In all of the higher Hymenoptera or Clistogastra, 

 active and aggressive characteristics are very prominent 

 in the behavior of the adult females, whatever may be 

 the food-habits of the larvae. Thus in the wasps, the 

 parent captures as prey suitable insects with which to 

 feed her larvsp, or to provision her nest, if her young are 

 to receive no post-natal care. In all cases she prepares 

 some sort of a cell or nest for her brood, and frequently 

 this requires marvelous skill in the selection of particular 

 materials and the collection of specific insects for food. 

 Where nests are provisioned in advance, the prey is 

 stung and paralyzed after a manner that requires very 

 complex instinctive behavior. If, on the other hand, we 

 look at the activities of the larva of one of the wasps 

 that stores a paralyzed insect away and places her egg 

 upon it, we see the larva consuming its food supply much 

 after the fashion of an externally feeding entomophagous 

 parasite. In fact, it is difficult to distinguish any really 

 fundamental differences. In each case the host is stung 

 and the egg attached to it, always externally by the wasp, 

 but sometimes externally also by the parasite. The wasp 

 paralyzes her prey, which the parasite does not do, as 

 her sting is not so severe, and she does not further bother 

 with the host insect. The egg of the parasite is deposited 

 at the time of stinging, and that of the wasp by a later 

 operation of the same organ, the ovipositor with which 

 she has previously paralyzed, but not killed, her prey. 

 Thus, aside from the maternal instincts, the entomophil- 

 ous wasp is scarcely more different from the ichneumon- 



