DEVELOPMENT OF CHALCIDS 331 



It is clear that this phase of parasitism differs somewhat 

 from ordinary epiparasitism. It has been called ' accidental 

 superparasitism ' by W. D. Pierce, quoted by Fiske (3), but 

 might better be termed ' metaparasitism '. Epiparasitism 

 then may be defined as successive infestations of a single host 

 by two or more species, or by several individuals of the same 

 species, of parasite. Metaparasitism is a development of 

 epiparasitism, and may be defined as the direct attack of one 

 epiparasite upon another. Objection may be taken that the 

 distinction is too fine to warrant the coining of a new word 

 in a science already burdened with technical names ; but of 

 late years the practice of introducing parasites to control 

 insect pests, in countries or continents where the latter have 

 become troublesome, has been much extended ; and, before 

 importing a parasite into a new area, it is of the first importance 

 to ascertain to what extent it is potentially metaparasitic upon 

 other species. 



Thus, suppose that two forms of primary parasites A and B 

 are imported into a certain locality. There will be a slight 

 reduction of their total efficiency, in proportion to the incidence 

 of epiparasitism between them ; but as long as plenty of hosts 

 are available, the loss due to this will be small, and in any case 

 little harm will result, as a pest destroyer will be reared 

 ultimately. But supposing that B is potentially metaparasitic, 

 while A is not, then in course of time, B, since it will always 

 be successful in contest with A, will reduce the latter species, 

 or even supplant it altogether. The mischief will be even 

 greater from an economic standpoint, if B should prove to be 

 less efficient than A in destruction of the host pest. 



In fact, this is what has actually taken place in Hawaii, 



Eucyrtus aphidivorus, Mayr., which like Charips is an endo- 

 parasite of Aphidius; but as its other bionomical relations are not 

 known, it has not been included m this discussion, and the same a2)plies 

 to other Chalcidae, recorded as reared from Ai)hides, but many, if not all 

 of which, are probably hyperparasites. However, as Arrow (' Entomolo- 

 gist's Monthly Magazine ',vol. Ivii, (September 1921) observed Aphelunis 

 chaonia, Wlk., ovipositing in aphides, this form may prove to be 

 a primary parasite. 



