1 96 DIPTERA OF NORTH AMERICA. [PART II. 



Gen. XXXIV. PtAGIONEURlJS. 



This genus has been established by me (in the "Wien. Entom. 

 Monatschr. I, 43) on the species described below, and known as 

 yet only in the female sex, but the extraordinary and peculiar cha- 

 racters of which rendered the establishment of a new genus neces- 

 sary. The whole habitus approaches the species of Gymnopter- 

 nus and Pelastoneurus most, differs, however, from both by the 

 first joint of the antenna? being entirely without hairs and by the 

 posterior transverse vein having an unusually oblique position ; 

 from Gymnopternus it differs moreover by the course of the last 

 segment of the fourth longitudinal vein, which is almost like that 

 of the genus Pelastoneurus. The peculiarities of the female 

 seem to indicate that the hypopygium of the male is disengaged. 



The establishment of the characters of this genus on so scanty 

 materials presents many difficulties. I believe, however, that the 

 following may be regarded at least as a temporary definition. 

 The first joint of the antennae without hairs, the second not reach- 

 ing thumb-like over the third, on the upper side much longer 

 than on the under side; the third joint short, without distinct 

 hair and with a dorsal arista. The posterior transverse vein very 

 oblique ; the last segment of the fourth longitudinal vein runs 

 much forward in its second portion and ends in the vicinity of the 

 third longitudinal vein, so that the first posterior cell becomes 

 very narrow near its end. The first joint of the hind tarsi is 

 without bristles. 



The name of the genus (from *xaytoj, oblique, and vtvpw, the 

 nerve) has reference to the extraordinary obliqueness of the pos- 

 terior transverse vein. ' ' 



1. P. linivittatns LOEW. 9 . Viridis, thoracis vitta media abdo- 

 minisque fasciis latis purpureis, antennis pedibusqne nigris, femoribus 

 virescentibus, genibus tibiarvuuque anteriorum basi testaceis, alia 

 cinereis. 



Green, middle stripe of the thorax and broad bands of the abdomen of a 

 purple color ; antennae and feet black, the knees and the basis of the 

 four anterior tibise dusky yellow ; wings gray. Long. corp. 0.25. Long. 

 al. 0.230.24. 



SYS. Plagioneurus univittatus LOEW, Wien. Ent. Mon. I, 43. LOEW, Neue 

 Beitr. VIII, 69. 



