26 XOKTH AMERICAN DIPTERA 



76. Some or all of the tibiae with preapical dorsal bristle 77 



Tibiffi without preapical bristle 80 



77. Postocellar bristles parallel, divergent or absent 78 



Postocellar bristles convergent (p. 315) LAUXANIID.5: 



78. Clypeus never prominent; femora with bristles 79 



Clypeus very prominent; femora without bristles, (p. 382) DRYOMYZID^ 



79. Ovipositor flat and wide; front long and moderately narrow; head short, 



hemispherical, the antennae never porrect; shining blackish flies. 



(p. 298) LONCH^ID^ 

 Ovipositor not prominent; front wide; head more or less orbicular or 

 the front produced; antennae usually porrect; very rarely shining 

 black (p. 367) TETANOCERID^ 



80. Antennae situated on the eye-stalks or at their base. (p. 358) DIOPSIDiSJ 

 Antennae situated on the front, though widely separated, regardless of 



the presence of eye-stalks 81 



81. Ocelli absent (p. 268) PYRGOTID^ 



Ocelli present 82 



82. Postocellar bristles convergent or absent 83 



Postocellar bristles divergent or parallel 84 



83. Posterior femora swollen and spinose beneath; abdomen clavate; small, 



slender flies (p. 373) MEGAMERINID^ 



Posterior femora not swollen and spinose; abdomen short and rather 

 broad, never clavate (p. 365) CHAM^MYID^ 



84. Presutural dorsocentrals absent or the subcostal and first veins end 



far apart (p. 271) OTITID^ 



Presutural dorsocentrals present or the thorax bearing very long, 

 fine pile (p. 296) PALLOPTERID^ 



85. Metascutellum developed, appearing as a strong convexity below the 



scutellum; hypopleura with strong bristles (p. 415) TACHINIDiS] 



Metascutellum weak or absent, or if developed there is only hair on the 

 hypopleura 86 



86. Oral opening and mouth parts very small; hypopleura with abundant 



long hair 87 



Oral opening normal; hypopleura with a row of bristles or only short, 

 sparse hair 88 



87. Scutellum extending far beyond the base of the metanotum; metascu- 



tellum never developed.." (p. 411) CUTEREBRID^ 



Scutellum very short; metascutellum usually strongly developed; palpi 

 usually large (p. 413) CESTRID^ 



88. Hypopleura with a row of bristles 89 



Hypopleura with fine, short hair or bare 90 



89. Apical cell strongly narrowed apically (p. 402) METOPIID^ 



Apical cell not at all narrowed apically (p. 384) MUSCIDjaC 



90. Oral vibrissae absent; mesonotum without bristles except above the 



wings (p. 374) PSILID^ 



Oral vibrissae present; mesonotum with bristles (p. 384) MUSCIDi9i] 



