Syrphus. 273 



2. Thorax with two grey lines on the front part 1. albostriatus. 



— Thorax without obvious lines 3. 



3. Band on third abdominal segment the broadest 2. tricinctus. 



— Abdominal bands about equal 4. 



4. Abdominal bands separated into spots (in macularis the 



spots may be just touching) 5. 



— Abdominal bands on third and fourth segments entire .... 7. 



5. Antennæ partly reddish; scutellum more or less yellow- 



haired ; abdominal spots going over the margin 3. venustus. 



— Antennæ all or nearly all black, scutellum black-haired . ... 6. 



6. Abdominal spots lunulate, not reaching the side-margin 4. lunulatus. 



— Abdominal spots somewhat semicircular, going over the 

 side-margin 5. macularis. 



7. Gubital vein dipped down over the first posterior cell; 



thorax shining 6. annulipes. 



— Gubital vein not dipped; thorax dull 7. torvus. 



8. Abdomen more or less ovate 9. 



— Abdomen quite or almost quite parallel-sided, often some- 

 what long 22. 



9. Abdomen with only basal spots and one foUowing band, 

 (sometimes the second band may be wanting, or on 



the contrary a narrow third band may be present). . . 21. bifasciatus. 



— Abdomen with at least basal spots and two following 



bands 10. 



10. Middle bands of abdomen (normally) uninterrupted but 



often emarginate 11. 



— Middle bands of abdomen (normally) separated into spots 



(conf. corollae) 19. 



11. Episloma with a black middle line; smallish species 12. 



— Epistoma without black middle line, only the central 



knob may be darkened 13. 



12. Antennæ more or less yellowish; anterior tarsi yellow; 



hind femora of female pale at base 10. annulatus. 



— Antennæ black; anterior tarsi dark; hind femora of 



female all black 11. lineola. 



13. Antennæ quite dark or black 14. 



— Antennæ more or less yellow, at least beneath the base 



of third joint 15. 



14. Frons black-haired, with a black spot above the antennæ; 



femora black at the base 12. grossulariae. 



— Frons yellow and yellow-haired ; femora quite yellow. . 13. diaphanus. 



15. Thorax dullish; scutellum black-haired 16. 



— Thorax shining 17. 



16. Larger species; the short hairs on anterior side of the 

 apical part of hind femora black ; hind femora of female 



all yellow 8. ribesii. 



— Smaller species ; the short hairs on anterior side of the 

 apical part of hind femora all, or almost all, yellow; 



hind femora of female black with yellow apex 9. vitripennis. 



17. Antennæ yellow; abdomen not marginale, the bands 



18 



