Syrphidae. 39 



2. Abdomen witli four normal segments in both sexes, 



second and third equal and long, fourth very small ^ 



(figs. 9 and 10) 2. Trighjphus. ^ "i- 



— Abdomen with four normal segments in the male, 

 five in the female, second to fourth about equal 



(figs. 25 and 26) 3. 



3. Outer top angle of first posterior cell about rect- 



angular (except in Heringi); third antennal joint _ 



more or less elongate; frons not conically projecting 3. Pipizella. ^ (, 



— Outer top angle of first posterior cell acute; third 

 antennal joint short, rarely a little longer 4. 



4. Frons somewhat conically protruding, frontal triangle 

 in the male small, not arched (figs. 23 and 24), 

 frons of female with side dust spots ; abdomen mostly 



spotted 6. Pipiza. IS^ 



— Frons not conically protruding, frontal triangle in 

 the male rather large and arched (figs. 19 and 20); 

 frons of female with or without side dust spots; 

 abdomen unspotted 5. 



5. Middle coxæ and hind trochanters in the male with 

 a spine ; frons of female with a transverse depres- 

 sion and abdomen somewhat pointed 5. Cnemodon. Hq 



— Coxæ and trochanters unarmed; frons of female ' 

 without transverse depression and abdomen less 



pointed 4. Penium. (^*^ 



6. Epistoma not hollowed below the antennæ, arched 

 or a little keeled, with a small central knob, partly 



or wholly yellow 1. Paragus. ^ ^T 



— Epistoma hollowed below the antennæ, with a central 

 knob or with the lower part produced, or both with 

 central knob and produced mouth edge 7. 



7. Entirely dark, black or metallic species with no pale 

 markings on head or body (only in a single case 

 abdomen with glaucous spots, Chilosia maculata) 8. 



— Not entirely dark species, but more or less with 

 pale parts or markings on head, thorax, scutellum 



and abdomen 9. 



8. More or less metallic species; eyes in the male 

 touching or separated ; frons of the female with 

 cross-furrows; epistoma in the male with or with- 

 out central knob, in the female without central knob 

 but more or less projecting at the mouth edge; 

 eyes bare; no eye-margins; scutellum without fringe 



below the margin 7. Chrysogaster.Oj d- 



— Black or æneous or bluish species, not, or not 

 distinctly metallic; eyes always touching in the male; 

 epistoma with central knob (except in maculata) ; 

 eyes often hairy, distinct eye-margins present; scu- 

 tellum with a marginal fringe below 8. Chilosia. j Z-l- 



