28 DURHAM DIPTERA. 



29 (28). Costa continued round the hind margin (V. 2). 



30 (31). Squamae very large. Tabanid^e (XVI.) 



31 (30). Squamae very small. 



Xylophagus, Mg. (XVII. 164). 



32 (27). Third joint of antennae not ringed (III. 10-55). 



33 (55). Arista or style terminal or wanting (III. 10-26, 



28-32, 35-4o, 48). 



34 (46). V.3. forked (V. 3-10, 13). 



35 (45). O.6 1 long, extending to, or nearly to, the hind margin, 



or entirely wanting (V. 3-9, 13). 



36 (39). Empodium much enlarged, giving the appearance of 



three foot-pads (VI, 9). 



37 (38). Squamae small, not covering the halteres, O.6 1 long 



and distinct (V. 3). Long bodied flies, head of 

 normal proportions. Leptid^e (XVII.) 



38 (37). Squamae very large, hiding the halteres, O.6 1 absent 



(V. 13). Short round-bodied flies, with very small 

 heads. Cyrtid^e (XXII.) 



39 (36). Empodium small, only two foot-pads apparent (VI. 



10, n). 



40 (41). Vertex hollowed out between the eyes (VI. 28). 



Asilidje (XVIII.) 



41 (40). Vertex flat or raised, eyes not protruding. 



42 (43) (44). V.4. ending in three branches at the margin, 



between V.3. and V.5. (V. 6, 7). 



BOMBYLIDiE (XIX.) 



43 (42) (44). V.4. ending in four branches at or near the 



margin, between V.3. and V.5. (V. 8). 



Therevim; (XX.) 



44 (42) (43). V.4. ending in two branches at the margin, 



between V.3. and V.5. (V. 9). Antennae without 

 a style (III. 23). Scenopinim: (XXI ) 



45 (35). O.6 1 short, not nearly reaching the hind margin 



(V. 10). Empire, part (XXIII.) 



46 (34). V.3. not forked (V. n, 12, 14-17). 



47 (52). Alulae absent or rudimentary. 



48 (51). Apex of the wing rounded. 



