DIPTEEA. 353 



30. Thoracic dorsum covered with thin white dust, front densely silvery- 



pollinose (Mex.) argentatus, sp. n. 



Thorax and front mostly shining 31. 



31. Costa with a row of erect cilia 32. 



Costa without cilia 33. 



32. Second joint of the fore tarsus shorter than any of the following joints 



(U.S.) *. [ciliatus, Loew.] 



Second joint of the fore tarsus longer than any of the following joints 



(Mex.) hirtipes, sp. n. 



33. Middle metatarsi with erect cilia above (Mex.) ciliipes, sp. n. 



Middle metatarsi not so ciliated 34. 



34. Middle tibise yellow, colour of body purple (Mex.) purpureus, sp. n. 



Middle tibiae yellow, colour of body green (Mex.) forcipatus, sp. n. 



Middle tibiae black (U.S., W.I.) ■ chrysoprasius, Walk. 



35. Wings with dark markings 36. 



Wings wholly hyaline 44. 



36. Antennae yellow (Brazil, Mex.) basilaris, Wiedem. 



Antennae black 37. 



37. The hyaline space between the cross-bands extending forward to the 



second vein 38. 



Hyaline space not reaching beyond the third -vein 40. 



38. First joint of fore tarsus white at tip, the following joints black, the 



4th fringed above with black (Mex.) interceptus, sp. n. 



Fore tarsi plain, gradually infuscated 39. 



39. Fore coxae black (Mex.) pennifer, sp. n. 



Fore coxae yellow (Mex.) flavicoxa, sp. n. 



40. Cilia of tegulae pale on lower half, third vein curved forward at the 



tip (Brazil) [imperator, Aldr.] 



Cilia of tegulae black 41. 



41. 2nd and 3rd joints of fore tarsi short, swollen, bristly (Mex.) . . . clavipes, sp. n. 

 Fore tarsi plain or only bristly 42. 



42. Fore coxae green (U.S.) [viridicoxa, Aldr.] 



Fore coxae pale 43. 



43. Middle metatarsus with a row of erect cilia on the fore side (U.S.) . . [scaber, Loew.] 

 Middle metatarsus plain (U.S.) [sipho, Say.] 



44. Face with numerous pale hairs (U.S.) [flavipes, Aldr.] 



Face bare 45. 



45. Middle metatarsi greatly elongated, ciliated (Antilles) [insularis, Aldr.] 



Middle metatarsi plain, short (Mex.) tonsus, sp. n. 



1. Psilopus bifimbriatus, sp. n. 



S . Face metallic blue, the lower half with white dust ; front deeply excavated, rather narrow, at the margin 

 of the eye on each side with conspicuous white hairs ; antennae small, black, second joint with few and 

 small bristles, arista small ; lower part of the orbit with long white hair. The front and vertex have a 



biol. centr.-amee., Dipt., December 1901. 2 z 



