168 ' [J"^y' ^^°*- 



44 (45) Third joint of antennae abruptly dilated at its base, and then almost 



excised beneath, long in both sexes ; abdomen rather short ; hind 

 coxse with a conspicuous black bristle 20. Machcrrium Hal. 



45 (44) Third joint of antennae not abruptly dilated about its base ; antennae of 



female short. 



46 (47) Hind coxae without any distinct black bristle (except in P. niicans) ; third 



joint of antennae moderately elongate (^), being not more than three 

 times as long as deep ; larger, hairier species... 



21. Porphyrops Meig. 



47 (46) Hind coxae with one distinct black bristle (except in the section with frons 



glossed with white) ; third joint of antenna3 remarkably elongate {S ), 

 being 6 — 10 times as long as deep (4 times in X. brevicorne) ; small, 

 moderately hairy species 22. Xiphandrium Lw. 



48 (41) Hypopygium pedunculate, free 23. Si/stenus Lw. 



49 (40) Second antennal joint inserted like a thumb into the third ; acrostichal 



bristles hardly more than a single row 24. Syntormon Lw. 



50 (37) Colour not metallic green or blue (sometimes rather metallic in Medeterus, 



but then antennae short and rounded at tip) ; anal vein absent or weak. 



51 (52) Third joint of antennae ovate, acute ; arista subapical ; anal vein absent; 



preapical bristle distinct ; hypopygium short 25. Achalcus Lw. 



52 (51) Third joint of antennae short and rounded; arista apical; preapical 



bristle absent; hypopygium disengaged, long and conspicuous... 



26. Medeterus Fisch. 



53 (2) Acrostichal bristles not in two rows, being either in one row ol" irregular. 



54 (55) Antennae long ((^), arista apical (subapical in <S. tarsatns) ; second joint 



of antennae inserted like a thumb into the third (conf. 3^. Bathy- 

 cranium) 24. Syntormon L^f. 



55 (54) Antennae short, arista dorsal (subapical in 34 Bathy cranium). 



56 (61) Discal cross-vein as long as, or longer than, last piece of postical (fifth) vein. 



57 (58) Front femora beneath with remarkably long spines 27. Scellus'Lvf. 



58 (57) Front femora beneath without, or with only short, spines. 



59 (60) Front femora thickened at base and ( (J) with shurt spines beneath... 



28. Hydrophorus Fall. 



60 (59) Front femora not thickened at base nor spinose beneath... 



29. Liancalus Lw. 



61 (56) Discal cross-vein shorter than last piece of postical (fifth) vein. 



62 (65) Abdomen depressed ; face contracted below antennae, but widening to- 



wards mouth. 



63 (64) Acrostichal bristles existing ; wings of normal shape ; legs ( ^ ) usually 



contorted or ciliated 30. Campsicnemus Walk. 



64 (63) Acrostichal bristles absent; wings nincpin shaped (<?); legs almost 



simple 31. Ectomus Mik 



65 (62) Abdomen compressed ; face either equally wide or narrowed towards 



mouth. 



66 (69) Antennae and abdomen entirely, or almost entirely, dark coloured. 



67 (68) Frons metallic ; costa (<J) with a long black swelling... 



32. Teuchophoriis Lw. 



