REVISION OF THE TWO-WINGED FLIES OF THE 

 FAMILY CLUSIIDAE. 



By A. L. Melander and Naomi George Argo, 



Of the State College of Washington, Pullman. 



The family Clusiidae, sometimes called the Heteroneuridae or 

 the Clusiodidae, is generally regarded as one of the rarer groups of 

 the Diptera. Seldom are its members met with in more than solitary 

 individuals. In our experience in collecting a hundred thousand 

 specimens of Diptera but a few dozen representatives of Clusiidae 

 have been encountered. 



Previously there have been described from the entire world 13 

 valid genera and 55 species. Aldrich's Catalogue in 1905 listed but 

 2 genera and 12 species as known from North America. The sub- 

 sequent publications of Johnson and Malloch have added 11 recog- 

 nized new species to the American list. Fifteen species have been 

 described from Europe and the same number from South America, 

 while four species have been recorded from the islands south of Asia. 

 The material secured for the present study, amounting to some 400 

 specimens, has produced 52 species, of which 25 are new. With the 

 extension in distribution of species originally described from Europe 

 or South America there are now known to occur in North America, 

 including Central America, a total of 58 species belonging to 7 genera. 

 Thus in its present status the family includes 80 recognized species 

 distributed among 13 genera. 



The Clusiidae are restricted in their distribution to Europe, North 

 and South America, and the East Indies. No species have been 

 described from Africa, Australia, or Asia, but there is mention by 

 Lefroy of the occurrence of an undetermined species in India. 

 Judging from the material at hand, the members of this family are 

 more abundant both in individuals and in species in Neotropical 

 than in either the Palaearctic or Nearctic regions. 



In most of the literature dealing with this group of insects the 

 family designation "Heteroneuridae" has been used. Coquillett 



No. 2501.— Proceedings U. S. National Museum. Vol. 64. Art. II. 



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