52 NOHTH AMERICAN DIPTERA. 



9. Front of female as broad as long, the callus transverse. 



II^MATOPOTA Meigen. 

 Front of female narrow. . . . DIACIILORUS Osten Sacken. 



10. Front tibise much dilated; process of the third joint much elongated 



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

 Front tibiae not dilated. . '. J 11 



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



America) v . DICHELACKRA Macquart. 



First antennal joint short ; body not elongate 12 



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



THEKIOPLECTES Zeller. 

 No ocelligerous tubercle 13 



13. Eyes pubescent ATYLOTUS Osten Sacken. 



Eyes bare TABANTS Linne. 



17. 



Species of moderate 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 \ipon a rounded tubercle ; front with 

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

 the third usually more or less elongated, and with or without 

 a terminal style or bristle, the style sometimes thickened and 

 forming one or two apparent antennal joints. 1'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 hypopygium or oviduct usually prominent. 

 Legs strong, bristly, of moderate length, rarely somewhat 

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

 rarely rudimentary. Tegulae small. Wings when at rest 

 lying parallel over the abdomen; basal cells long; two or 



