JOU RNAL 



o I Mil-: 



J}f\a ]9orh ^Intomologiral ^oriptg. 



Vol. II. SEPTE:M]5ETI, 1894. Ko. 3. 



REVISION OF THE DIPTEROUS FAMILY 

 THEREVIDiE. 



By I). \V. Co(^uiLLEi 1', Washington, I). C. 

 In Osten Sackeii's Catalogue of the Diptera of North Anierica, 

 four Therevid genera are credited to our fauna : Psilocephala, 

 T/iereTa, Xcstomyza and Tabuda. The genus Xestomyza, however, 

 is not at present known to occur in our fauna, the single species 

 heretofore referred to it {X. planici-ps Loew) differing from it in so 

 many important characters as to necessitate erecting a new genus 

 for its reception ; the principal differences are : the much shorter 

 proboscis; the first posterior cell bisected by a crossvein, and the 

 widely opened fourth i)osterior cell. The examination of (|uite a 

 large series of specimens shows lliese characters to be constant, 

 and for this new genus I would propose the name o^ Mtidp/iriii^nia. 

 Our genera, including a second new one, discovered by the 

 writer, may be tabulated as follows: 



1. First posterior cell entire, never bisected by a crossvein ... 2 

 First posterior cell divided by a crossvein into two cells ; fust antennal joint 



unusually large .... Metaphragma, gen. nov. 



2. Head nearly twice as broad as long, vertical diameter of eyes nearly twice 



their horizontal diameter ....... 3 



Mead not as broad as long, vertical diameter of eyes equalling their horizontal 

 diameter, first joint of antenn.v unusually large and 

 polished Nebritus, gen. nov. 



3. Face hairy .........-•• 4 



Face bare Psilocephala. 



4. Third joint of antenna.- at least two-thirds as long as the first Thereva. 

 Third joint of antennii; one-third as long as the unusually large 



first joint, scarcely longer than broad . . . Tabuda. 



Metaphragma, gen. nov. 



Head nearly twice as broad as long, eyes of male separated as widely as the 

 two posterior ocelli ; first antennal joint unusually robust, nearly as long as the 

 head, nearly three times as long as the third joint, the latter only slightly wider 

 than the second, destitute of bristles ; style apical, distinct, two jointed ; face very 



