390 



NORTH AMERICAN DIPTERA 



38. 



39. 



40. 



Anal vein extending to the margin of the wing, at least weakly 39 



Anal vein never extending to the margin of the wing 75 



Under surface of the scutellum with fine, soft, erect hairs 51 



Under surface of the scutellum bare 40 



Three sternopleurals 44 



Two sternopleurals (cf. Fucellia) 41 



41. Upper apex of third antennal segmint acute or angulate; scutellum 



with four bristles 42 



Third antennal segment rounded apically; scutellum with one pair of 

 marginals 43 



42. Arista thickened on basal half, its penultimate segment much longer 



than wide (43) Pselaphephila Becker 



Arista thickened on basal fourth, its penultimate segment short. 



Chtetosa Coquillett 



43. Three pairs of postsutural dorsocentral bristles. .. .Hexamitocera Becker 

 Two pairs of postsutural dorsocentral bristles Cleigastra Macquart 



44. Scutellum with one or two pairs of marginal bristles; palpi without 



long outstanding apical bristle 45 



Scutellum with six marginals; palpi with strong apical bristle. 



Plethochaeta Coquillett 



45. First vein bare 46 



First vein setulose on apical third (38) Orthacheta Becker 



46. Anterior femora without strong bristles on the anterior surface 47 



Anterior femora with strong bristles on the anterior surface, propleura 



haired *Amaurosoma Becker 



* Cuiian. 1927, Can. Ent., lix, p. 293. 



MuscidsB II. — 17, Pentacricia aldrichi, cT abdomen; 18, Eremoniyia humeralis, H" abdomen; 

 19, Eremomyia humeralis; 20, Neodexiopsis ; 21, 22, Hammomja; 23, Coenosia, hind leg; 24, 

 Hylemya, abdomen; 25, Tetrachaeta unica; 26, Hoplogaster; 27, Pegomya bicolor; 28, 29, 

 Hydrophoria divisa; 30, Platycoenosia pokornyi ; 31, 32, Hylemya. 



