2 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.60. 



mal length and tapering off rather abruptly, ending in a short 

 tubercle; Bihio fratemus Loew, a specimen collected at Castle Eock^ 

 Pennsylvania, May 3, 1908 (H. S. Harbeck), has the basal fourth 

 of each hind tibia constricted, so as to form an extra joint in the leg, 

 imperfect on one side, but apparently perfect on the other. In this 

 connection it is worth recalling Dr. W. M. Wheeler's record* of an 

 antenniform appendage branching from a fore coxa of Dilophus 

 tibialis Loew. 



The writer is indebted for loan of material used in the present 

 study to Prof. J. M. Aldrich, curator of the Division of Insects, 

 United States National Museum. 



The location of types and other specimens is shown by names or 

 initials in parentheses after citation of locality records. Type locali- 

 ties of described species are named in brackets following bibliograph- 

 ical citations. 



KET TO OENEEA. 



A. Third longitudinal vein furcate (Pleciinae), 

 B. Fourth and fifth veins forked. 



C. Distance between anterior cross vein and fork of fourth vein more than 



twice length of cross vein ; antennae twelve-jointed Hesperimis 



CC. Distance between anterior cross vein and fork of fourth vein much less 

 than twice length of cross vein ; antennae 8- to 9-jointed. 

 D. Fork of third vein very long, beginning near anterior cross vein ; 



costal margin of wing sinuate Crapitula ^ 



DD. Fork of third vein much shorter, its origin remote from anterior 



cross vein; costal margin of wing not sinuate Plecia. 



BB. One or both of these veins not forked. 



B. Fifth vein not forked Penthetria.^ 



EE. Neither the fourth nor fifth veins forked Eupeitenus.* 



AA. Third longitudinal vein not furcate (Bibioninae). 

 F. Front tibia with two spurs at apex, the outer stronger. 



G. Third and fourth longitudinal veins coalescent for a short distance. 



Bibiodes. 

 GG. Third and fourth veins not coalescent, joined by the anterior cross 



vein Bibio. 



FF. Front tibia with two or three series of spines ; thoracic notum crossed 

 by two pectinate ridges Dilophus. 



^ Arch. f. Entw. Mech. d. Org., vol. 3, 1896, pp. 26,108, pi. 16. 



■■' Gimmerthal. An Asiatic genus ; characters used In key derived from Loew's figure, 

 Berl. Ent. Zeit, 1858, pi. 1, fig. 12. 



' Latreille. A European genus ; characters used in key derived from Melgen's figure, 

 Syst. Besch. Europ. zweifl. Ins., vol. 1, 1818, pi. 10, fig. 18. Loew (work cited, p. 105) 

 states that the venation in the sexes is alike and that consequently Meigen's figure 17 

 of the male is incorrect. 



* Macquart, not Serville, as the former writes ; he adopted a cabinet name of Serville, 

 but published the original drsciiption himself (Dipt. Exot., vol. 1, 1838, pp. 84-5).^ 

 Genotype Penthetria atra (Macquart, Hist. Nat. des. Insectes, vol. 1, 1834, p. 175) de- 

 scribed from Philadelphia, but no specimens have been seen by the present writer. 

 Characters used in the key derived from Macquart's figure (work first cited, pi. 12, fig. 3). 

 Van Der Wulp identifies P. atra from Wisconsin (Tijds. v. Ent., vol. 5, 1869, p. 80). 

 For description (as a new genus) of the fly identified as Eupeitenus by Coquillett sec. 

 Proc. Ent. Soc. Wash., vol. 23, 1921, p. 49. 



