52 XOKTII AMEUICAN DIPTERA. 



9. Front of femak' as broad as loiij;', tlic callus transverse. 



ILematopota Moigen. 

 Front of female narrow. . . . Diachlorus Osten Sacken. 



Ifl. Front tibia? niucli ililated ; process of tlie tliiid joint much elongated 



(Central and South America). . . . StibasoxMA Schiner. 



Front tibia^ not dilated. . . . . . . . .11 



11. First antennal joint elongate; body elongate (Central and Soutli 



America). ...... Diciielackra Macquart. 



First antennal joint short ; l)ody not elongate. .... 12 



12. A small oceliigerous tubercle present in the male; eyes pubescent. 



Thekioplectes Zellcr. 

 No oceliigerous tubercle. ........ V] 



18. Eyes pubeseeiit. ..... Atylotus Osten Sacken. 



Eves l)are. ........ Tabanms Linne. 



17. ASILIIX^. 



Sppcies of mo(ler;ite to large size, usually more or less elon- 

 gate in form, sometimes thickly hairy ; always bristly, the 

 bristles usually conspicuously strong; highly predaceous in 

 habit. Head flattened, broad and short, separated from the 

 thorax by a freely movable neck. Front excavated between 

 the eyes, the eyes in both sexes separated. Three ocelli pres- 

 ent, usually situated upon a rounded tuljercle ; front with 

 bristles. Antennae porrect, simple, composed of three joints, 

 the third usually more or less elongated, and with or Avithout 

 a terminal style or bristle, the style sometimes thickened and 

 forming one or two apparent antennal joints. I'roboscis 

 never elongated, firm and horny, adapted for piercing, directed 

 forward, or forward and downward ; palpi composed of one or 

 two joints ; labella not fleshy. Abdomen composed of eight 

 segments, the hypo])ygium or oviduct usually prominent. 

 Legs strong, bristly, of moderate lengtli, rarely somewhat 

 elongated; tarsi strong; empodia bristle-like, tlie pulvilli 

 rarely rudimentary. TeguliB small. Wings when at rest 

 lying }(arallcl over the abdomen; basal cells long; two or 



