FAMILY ASILID.E THE ASSASSIN FLIES 177 



51. No acrostical hairs (76, 112) *Metapojton Coquillett 



Acrostical hairs present, usually abundant but short (84, 99). 



fLasioposon Lcew 



52. Mesonotum with the hair appressed and usually with distinct, sub- 



appressed dorsocentral bristles posteriorly 53 



Mesonotal hair erect, the bristles, if present, very fine and erect 5G 



53. No trace of dorsocentral bristles (type Lasiopogon terricola Johnson) 



(84, 99) Alexiopogon, n. g. 



Distinct, though weak dorsocentrals posteriorly 54 



54. Abdomen elongate, more or less narrowed basally in the males 55 



Abdomen short and broad, rather strongly tapering in both sexes; hair 



rather abundant but short Pycnopogon Lcew 



55. Disc of scutellum with hairs toward either side (52, 126). .Callinicus Lcew 

 Scutellum with marginal bristles and hairs only (39). 



Chrysoceria Williston 



56. Face decidedly gibbous, the swelling clearly limited above 57 



Face flat or evenly, gently convex 58 



57. The third vein branches before the apex of the discal cell; style long 



(129, 151) JEucyrtopogon Curran 



The third vein branches conspicuously beyond the apex of the discal 

 cell; style short (128, 152) §Cyrtopogon Lcew 



58. Posterior tibiae strongly swollen, about twice as large as the anterior 



ones (78, 143) Holopogon Lcew 



Posterior tibiag not enlarged (57. 127) Heteropogon Lcew 



59. Antennae with a terminal arista 77 



Antennae with or without a terminal style which is never bristle-like . . 60 



60. Wing with only two submarginal cells 61 



Wing with three submarginal cells (23, 62) Pogonosoma Rondani 



61. Third antennal segment with an apical style, which is rarely difficult 



to discern 62 



Third antennal segment without style 66 



62. Third antennal segment excised and bearing a very short bristle be- 



yond the middle on the upper side, the style slender (66, 108). 



Atractia Macquart 

 Third antennal segment not excised above 63 



63. Face with strong, isolated bristles and short, fine hair 65 



Face with soft hair, which may be long and contain some coarse ones. . 64 



64. Face perpendicular, more prominent above or almost evenly convex; 



mesonotum not with dense, long yellow pile (9, 73, 92). 



^Laphystia Lcew 

 Face most prominent below the middle, strongly convex; mesonotum 

 with dense, long yellow pile (24) Dasylechia Williston 



* Melander, 1923, Psyche, xxx, p. 210. 



t Melander, 1923, Psyche, xxx, p. 136. 



t Curran, 1923, Can. Ent. Iv, p. 95. 



§ Curran, 1923, Can. Ent. Iv, p. 123 ; Melander, 1923, Psyche, xxx, p. 102. 



i Curran, 1931, Amer. Mus. Novit. No. 487, p. 11. 



