SiUl'lllN.K. 29 



6. Face with central knob, seldom con- 



siderably produced at upper mouth- 

 edge 7. 



Face without central liuob, generally 

 mucli produced at upper mouth- 

 edge 18. 



7. Abdomen conspicuously constricted at 



base Baccha, Fabr., p. 1 1 •!. 



Abdomen not conspicuously constricted 

 at base 8. 



8. Face and scutellum ■wluJlv a-neous or 



black * " !». 



Face partly yellowish* 10. 



9. Front' tibia; 'or tarsi dihxted in J; in $ [et Serv., p. 52. 



simple Platyohirus, St. Farg. 



Front tibia> and tarsi simple in c5' and § Mfxanostoma, Sch., 



10. Thorax with conspicuous yellow side [p. 40. 



lines ; pleurae also with yellow marks. 11. 

 Yellow side lines on thorax incon.^picu- 

 ons or absent ; pleurte without yellow 

 marks '. 12. 



11. Abdomen ralatively broader, about as [p. U4. 



wide as thorax Xaxtiiogramma, Sch., 



Abdomen relatively narrower, always [et Serv., p. 99 f. 



narrower than thorax Spii.'EROPHORiA,St. Farg. 



12. Abdomen with sharply-defined yellow 



bands or pairs of yeUow spots or 



lunules 13. 



Abdomen without such yellow marks . . 17. [p. 66. 



13. Frons inflated ' Lasiopttcus, Rond., 



Frons not inflated 14. 



14. Third longitudinal vein dipped down- 



wards into 1st posterior cell 16. 



Third vein not dipped downwards (rare 



exceptions i l-"). 



16. Frons less abruptly produced into an 



antennal prominence ; mouth-opening 



short and oval : ocelli placed near 



vertex Syri'HUS, Fabr., )>. U'.». 



Frons rather abrnptly produced into an 



obtuse antennal prominence ; (abdo- 

 men broader and flatter than in 



Si/r/i/nis ; facial bump more ])rominent 



than in Si/rphus, and sul)marginal cell 



a little broadened at niiddli' and tip); 



mouth-o])ening narrow and linear; 



oceili ]ilaced at some distance from 



vertex Asaucina, Macq., \>. (53. 



16. Eyt-.s practically bare; 3rd vein well- 

 dipped \ DiDKA, Macq., p. '")«). 



Eyes closely pube.-ccnt ; 3rd vein niiuh 



less dipped I Diueoides, Bruu , p. 57. 



* Sonic care is requirod to decide these charueters. 

 t IsciiioDON, Sack, also fulls in this sectioa ; see p. 97. 

 J These sccoudHry chiirnctorfi are weak. 



