46 NORTH AMERICAN DIPTERA 



47. Cell 1st M2 closed; eastern Dicranota: Eudicranota subg. n. 



Cell 1st M2 open by atrophy of m 48 



48. Cell M, lacking Dicranota: Paradicranota subg. n. 



Cell Ml present Dicranota: Dicranota Zetterstedt 



49. Cell 1st M2 closed; eastern Dicranota: Amalopina Brunetti 



Cell 1st M; open by atrophy of m 50 



50. Cell Ml lacking (2) Dicranota: Plectromyia Osten Sacken 



Cell Ml present Dicranota: Rhaphidoiabis Osten Sacken 



HEXATOMINI: SUBTRIBES, GENERA, SUBGENERA 



51. Antennas with not more than 12 segments (Hexatomaria, Hexatoma). 52 

 Antennae with more than 14 segments 54 



52. Cell 1st M2 open; two branches of M reach the wing-margin (31); 



eastern Hexatoma: Hexatoma Latreille 



Cell 1st M2 closed; three or four branches of M reach the wing- 

 margin (32) 53 



53. Feet snowy- white; eastern and tropical. .Hexatoma: Penthoptera Schiner 

 Feet not white (32) Hexatoma: Eriocera Macquart 



54. Wings with only two branches of Rs present; vein R2 lacking 55 



Wings with three branches of Rs present; vein R2 presei*ved (except 



in Phyllolabis) 5G 



55. Rostrum elongate, exceeding one-half the length of the entire body 



(33) ; (Elephantomyaria) Elephantomyia Osten Sacken 



Rostrum short and inconspicuous, not exceeding the remainder of head 

 (34); eastern and tropical (Atarbaria). 



Atarba: Atarba Osten Sacken 



56. Apical cells of wing with macrotrichia 57 



Cells of wing without macrotrichia (excepting in stigmal area) 61 



57. A supernumerary crossvein in cell M; eastern (Limnophilaria). 



Limnophila: Trichephelia Alexander 

 No supernumerary crossvein in cell M 58 



58. Cell R3 of wings sessile, subsessile or short-petiolate; Rr+s+i lacking 



or much shorter than m-cu. (Limnophilaria) 59 



Cell Rs of wings long-petiolate, R2+3+4 being as long as or longer than 

 m-cu 60 



59. Wings with macrotrichia abundant, involving the cells basad of cord. 



Ulomorpha Osten Sacken 

 Wings with sparse macrotrichia in cells beyond cord only. 



Limnophila: Lasiomastix Osten Sacken 



60. Small species (wing, 0", less than 5 mm.); cell Mi usually present; an- 



tennae short in both sexes (Adelphomyaria) . . . . Adelphomyia Bergroth 

 Larger flies (wing, c^", over 6 mm.); cell Mi lacking; antennae of male 

 very long; tropical (Limnophilaria) Shannonomyia Alexander 



61. A supernumerary crossvein in cell C (Epiphragmaria). 



Epiphragma Osten Sacken 

 No supernumerary crossvein in cell C (35) 62 



