FAMILY ASILID.E — THE ASSASSIN FLEES 173 



21. Face wholly thickly pilose Ablautus Lcew 



Mystax limited to the lowest fourth of the face, the face sparsely 



"haired above (54, 100) Hodophylax James 



22. Anal cell absent, the wings extremely narrow at the base (140). 



Eurhabdus Aldrich 

 Anal, cell present 23 



23. Mesonotum without dorsocentrals in front of the middle 24 



Mesonotum with a pair of dorsocentrals in front of the middle. 



Schildia Aldrich 



24. Empodia entirely absent (147) Psilonyx Aldrich 



Empodia present, about half as long as the claws (1, 2, 3, 148, 149). 



Leptogaster Meigen 



25. Antennae with a slender terminal arista (4, 89) *Damalis Fabricius 



Antennse with or without a terminal style 26 



26. Only four posterior cells (93) Townsendia Williston 



Five posterior cells 27 



27. Head slightly higher than broad; face nai'row above, swollen and 



broadened below 28 



Head obviously broader than high 30 



28. Antennas with a terminal style 29 



Antennae without visible style; fourth posterior cell closed before the 



border of the wing (118) Ospriocerus Lcew 



29. Metapleura bare (6, 37, 130) fStenopogon Lcew 



Metapleura with hair or bristles (6, 37, 130) fScleropogon Loev/ 



30. Antennas apparently five segmented, the segments of the style simu- 



lating antennal segments 31 



Antennal style usually strongly differentiated from the third antennal 

 segment, absent, or the fifth segment longer than the second 33 



31. Third and fourth antennal segments very deeply emarginate apically 



(11) Myelaphus Bigot 



Third and fourth segments not concave apically 32 



32. Fifth antennal segment not longer than the second (103). 



Ceraturgopsis Johnson 

 Fifth antennal segment about as long as the third (10, 132). 



Ceraturgus Wiedemann 



33. Fourth posterior cell closed 34 



Fourth posterior cell open, rarely almost closed 40 



34. Face haired above the mystax 36 



Face bare except along the oral margin 3o 



35. Metanotal callosities bare (38, 136) Archilestris Lcew 



Metanotal callosities with hair or short bristles (7, 101) 



Microstylum Macquart 



36. First posterior cell closed and long petiolate (109) Triclis Lcew 



First posterior cell open or closed in the wing margin 37 



* Curran, 1930. Amer. Mus. Novit. No. 425, p. 5. 



t Bromley, 1931, Amer. Ent. Soc. Amer., xxiv, pp. 427-4?8. 



