AMERICAN DIFTERA. 273 



Pelastoneurus is wide and bulges below, while in Sarcionus it is nar- 

 row and does not bulge. 



To avoid mistakes of genei'ic reference, I have combined the 

 tables of the three genera. 



Combination Table of North A^nerican Species. 



1. Femora largely black 2. 



Femora yellow, or but little infnscated 10. 



2. First part of costa greatly thickened in the male, noticeably so in the 



female 3. 



First part of costa not perceptibly thickened 4. 



3. Tibise yellow (W. I.) Paracliu** abdouiiualis Aldrich. 



Tibiae black (La., N. Y., Cuba, Mex.). . Paraelius alboiiotatus Loew. 



4. Fore femora yellow, middle and hind ones with the apical third and half 



respectively black (Mex.) Paraelius f*ein<»i'atiis Aldrich. 



Fore femora black, with yellow ti|)s; middle black, with apical half yellow; 



hind ones yellow, with l)h(ck tijis (Cal.). 



Pelaiiilo near IIS dissiiiiilipes Wheeler. 

 Femora, at least of male, more uniformly black 5. 



5. Antenuje reddish, except the iippei' edge and tip; thoracic dorsum bright 



bluish green (W. I.) Paraelius fiiseieoriiis Aldrich. 



Antennae black 6. 



6. TibifB of male wholly black 7. 



Tibise of male largely yellow • • • 8. 



7. Upper half of the face bright green (Alex.). 



Pelastoueurus Iiaiuatus Aid. 

 Upper half of face with whitisli dust (W. I.-. .Paraelius nigripes Aid. 



8. Hypopygium small, rounded (Mex.) Paraelius hunieralis Aid. 



Hypopygium decidedly elongated 9. 



9. Face of male very narrow below (Tex.). . ■ -Paraelius puiiiilio Loew. 

 Face of male of uniform width (Fla.) Paraelius seutatiis n. sp. 



10. Wing of male with a rounded apical brown spot. (Hex.). 



Pelastoueurus bigeminatiis Aldrich. 



Wing in both sexes with several distinct brown spots 11. 



Wing not spotted, or with one or two spots on the veins 12. 



11. Fourth vein uniformly approaching the third (Mex.). 



Pelastoueurus puuelipenuis Say. 

 Fourth vein bent abruptly towards the third (Fla.). 



Pelastoueurus pietipeiinis Wheeler. 



12. A spot of white pollen on the posterior part of the thorax before the scutel- 



lum (N. Y., Cal., Fla.)- ■ ■ -Peliistoneurus longieauda Loew. 

 Without such spot 13. 



13. Antennal arista of male ending in a lamella 14. 



Antennal arista not ending in a lamella ; 15. 



14. Arista of male long, tapering, thin ( W. I.). 



Paraelius diseifVr Aldrich. 

 Arista quite short, thick (E. U. S) ... Paraelius elavieulalus Loew. 



TRANS. AM. KNT. SOC. XXX. (35) SEPTEMBER. 1904. 



