AMERICAN DIFTERA. 281 



27. Arista at least two-tliirds the leii,gtli of the entire body 28. 



Arista iniicl) shorter 30. 



28. Arista ending in a small disk, fore metatarsus not with long cilia above 



(Alex.) iiobilisKiiniiw Aid rich. 



Arista plain, fore metatarsus with long cilia above 29. 



29. Appendages of hypopygium pale, middle metatarsus also ciliated (U. S.). 



coniatiis Loew. 

 Appendages of hypopygium blackish, middle metatarsus plain (U. S.). 



criiiilus u. sp. 



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



nose (Mex.) argeiitatus Aldrich. 



Thorax and front mostly shining 31. 



31. Costa with a row of erect cilia 32. 



Costa without erect cilia 33. 



32. Second joint of fore tarsus shorter than any of the following (U. S.). 



{cUiafus Loew) iniin<Iii»> Wiedemann. 

 Second joint longer than any following (.Mex.) Iiirtipes Aldiich. 



33. Middle metatarsi with erect cilia above (Mex.)- cilii|>e!« Aldrich. 



Middle metatarsi not so ciliated 34. 



34. Middle tibiae yellow, color of body purple (Mex.). . . . piirpiireia!^ Aldrich. 



Middle tibiae yellow, color of body green (Mex.) f*4>rci|>atiiH Aldrich. 



Middle tibia; black (U. S., W. I.) olirystioprasius Walker. 



35. Wings with dark markings 36. 



Wings wholly hyaline 44. 



36. Anteunse yellow (Brazil, Mex.) basilai'is Wiedemann. 



Antennae black 37. 



37. The hyaline space between the crossbands extends forward to the second 



vein 38. 



Hyaline space not leaching beyond third vein 40. 



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



fringed above with black (Mex.) iiiterceptiiiii Aldrich. 



Fore tarsi plain, gradually infuscated 39. 



39. Fore coxse black (Mex.) peuiiifer Aldrich. 



Fore coxae yelllow (Mex.) flavicoxa Aldrich. 



40. Cilia of tegulae pale on lower half, third vein curved forward at tip (Brazil). 



iniperator n. sp. 

 Cilia of tegulae black 41. 



41. Second and thirds joints of fore tarsus stout, swollen, bristly (Mex.). 



elavipcN Aldrich. 

 Fore tarsi plain, or only bristly 42. 



42. Fore coxae greeu (U. S.) viridieoxa n. sp. 



Fore coxffi pale 43. 



43. Middle metatarsus with a row of erect cilia on fore side (U. S.). 



scaber Loew. 

 Middle metatarsus plain (U. S.) sipho Say. 



44. Face with numerous pale hairs (U. S.) (lavipew n. sp. 



Face bare 45. 



45. Middle metatarsi greatly elongated, ciliated (W. !.)• • . .insularis Aldrich. 

 Middle metatarsi plain, short (Mex.) tunsiis Aldrich 



TRANS. AM. ENT. SOC. XXX. (36) OCTOBER. 1904. 



