SERPHOID AND CHALCIDOID PARASITES OF THE HESSIAN FLY 3 



Among other early American writers who concerned themselves 

 with the subject of hessian-fly parasites, either by describing species 

 or recording observations on their habits and abundance, were Asa 

 Fitch, Thaddeus W. Harris, C. V. Riley, S. A. Forbes, G. H. French, 

 Benjamin D. Walsh, A. J. Cook, A. S. Packard, H. Osborn, L. O. 

 Howard, and F. M. Webster. Of these, Forbes and Riley probably 

 made the most important contributions, each having published de- 

 scriptions of several species and recorded important facts regarding 

 their habits and distribution In Europe, Fred Enock, Eleanor A. 

 Ormerod, and Karl E. Lindeman made important contributions to 

 the same subject. The studies by workers in the Bureau of Ento- 

 mology and by certain investigators in France and Russia since 1890 

 have added greatly to our knowledge of these parasites. Outstand- 

 ing contributions have been made in North America by W. H. 

 Ashmead, P. R. Myers, R. W. Leiby, C. M. Packard, C. C. Hill, W. R. 

 McConnell, W. J. Phillips, and E. G. Kelly; and in Europe Paul 

 Marchal's biological studies and the taxonomic work by N. Kurclju- 

 mov are especially important in this connection. Other workers, too 

 numerous to mention, have either published information of greater 

 or less importance or furnished such information to be published by 

 others. 



Of the 41 species treated herein, 5 are serphoids belonging to the 

 family platygasteridae while the others are all chalcidoids, of which 

 3 belong to the family Eurytomidae, 4 to the Callimomidae, 15 to 

 the Pteromalidae, 5 to the Eupelmidae, 1 to the Encyrtidae, 2 to the 

 Aphelinidae, and 6 to the Eulophidae. Thirty-five species are 

 known to parasitize the fly in America', 17 attack it in Europe, and 

 11 species are common to both continents. 



The disparity between the number of species attacking the fly in 

 North America and of those known to attack it in Europe is believed 

 to be due more to the fact that the parasites of this host have been 

 more thoroughly investigated in this country than abroad than to 

 any actual difference in the amount of parasitization. It is suspected 

 that several of the more important parasites in North America 

 which are at present not known to occur in Europe will eventually 

 be found there. Of the 6 European species which have not yet been 

 found in North America, only 1, Trichcosis remulus (Walker), 

 seems to be of much importance, if one may judge by the rather 

 meager records available. Not enough is known of the other five 

 species — Meraporws crassicornis Kurdjumov, Arthrolytus mxiculipen- 

 nis (Walker), Eupter ormolus micropterws Lindeman, Eupelmus atro- 

 purpureus Dalman, and E. karschii Lindeman — to warrant any posi- 

 tive statement regarding their effectiveness as parasites of the fly. 



HOST RELATIONSHIP 



It is interesting to note the host associations of the various para- 

 sites. Of the 5 species of Platygasteridae parasitic upon the hes- 

 sian fly, 4 species seem to be confined, very largely at least, to that 

 host, although 3 of these apparently do occasionally attack other 

 closely related dipterous insects that infest wheat or other grass and 

 grain plants. The fifth species is believed to be primarily a para- 

 site of the wheat midge, Contarinia tritici (Kirby), but at times 

 attacks the fly. The various species of Chalcidoidea in general seem 



