26 BULLETIN 116, UNITED STATES NATIONAL MUSEUM. 



50. Fifth joint of fore tarsi wholly black, rather small, with a finger-like app<^nda<:;e 



extendini,' over the claws (Louf-'iana) No 208, digitus, new species. 



Fifth joint of fore tarsi large, conspicuously tipped with white, or with the empo- 

 dium large and white 51 . 



51. Fifth joint of fore tarsi with an appendage resembling a sixth joint, both tipped 



with white (District of Columbia; Louisiana; Illinois). 



No. 203, serarticulatus Loew. 



Fourth and fifth joints of fore tarsi of about equal size, black; fifth joint with a 



white extension nearly as large as the join^ itself, formed by the enlarged 



empodium (Texas) No. 204, aphaeristes Brues. 



52. Hind femora ciliated below; front in both species either green or violet 53. 



Hind femora without cilia 54. 



53. Humeri more or less yellow; cilia of hind femora shorter than the width of the 



femora (widespread) No. 179, scapulans Loew. 



Humeri metallic; cilia of hind femora longer than the width of the femora (New 

 Jersey; New. York) No. 180. domesticus, new species. 



54. Arista tipped with a lamella (Washing;ton; Alaska) No. 109, hastatus Loew. 



Arista plain 55. 



55. Middle tarsi compressed and widened (widespread) No. 181, latipcs Loew. 



Middle tarsi plain 56. 



56. Wings with a deep sinus between the tips of fifth and sixth veins 57. 



Wings normal in outline 58. 



57. Wings with only a small incision at tip of fifth vein (Illinois; New Hampshire; 



New York) No. lSl,fulvipes Loew, 



Wings with a deep incision at tip of fifth vein, which causes a distinct lobe just 

 basallyof fifth vein (North Carolina) No. 175, carolinensis, new species. 



58. Costa not thickened at tip of first vein; face silvery (New York). 



No. 205, terminalis Loew. 

 Costa a little thickened from the tip of first vein, tapering nearly to its tip; face 



yellow (Tennessee; Kansas) No. 174, aurifacies Aldrich. 



Costa with a conspicuous, elongated, knot-like enlargement at tip of first vein. 59. 



59. Hypopygium very small, its lamellae not developed (Illinois). 



176, imperfectus, new species. 

 Hypopygium and its lamellae normal (Eastern States) No. 177, vittatus Loew. 



FEMALES (Synopsis). 



A*. All femora black, at least on basal half. 



Bi. All tibiae black 3. 



B*. Anterior tibiae yellow and sometimes the others also. 

 C^ Inferior orbital cilia black. 



D^ Fore tibiae yellow, middle mostly, hind ones wholly black 28. 



D^. Four anterior tibiae yellow 34» 



D^. All tibiae yellow, hind ones may be black at tip 43» 



C^. Inferior orbital cilia pale 47 . 



A''. Middle femora mainly yellow, anterior and posterior ones black on basal half 



or more 63. 



A^. Anterior and middle femora yellow, posterior ones black 67. 



A*. Middle and posterior femora yellow, anterior ones largely black 68. 



A^. All femora yellow, extreme base or tip may be blackened. 



B'. Orbital cilia wholly black 72. 



B^. Inferior orbital cilia pale. , 



C. Cilia of the calypters pale. 



D'. First antennal joint black at least above 84. 



D^. Antennae yellow, at least the first joint wholly yellow 102. 



