510 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 113 
Alaska, 21 July 1921, by J. M. Aldrieh. This tentative determination 
is the only record of A. atricornis Meigen in North America. 
10. 
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12. 
13. 
14. 
15. 
16. 
1 We 
Subfamily Heleomyzinae 
Key to the Genera of Heleomyzinae 
. Costal spines and dorsal preapical bristles of tibiae absent or inconspicuous. 2 
Costal spines and dorsal preapical bristles of tibiae present. . .. . 3 
. Posterior portion of mesopleuron with bristle present. . Borboropsis o 51 1) 
Posterior portion of mesopleuron bare. .... . Oldenhergiclin (p. 512) 
se rosternal bristles absent: | 609 205 be. ef oye) ee ol ler ge 8 
Prosternal bristles present . . . wt glen Siete. ey Loe astosisl VGnins depen Orem E 
Midtibiae with 1 ventral apical brictle TPM ER oer Or cae dao 6 0 E 
Midtibiae with several ventral apical bristles. . ........2.2..7 
. First vein ending distinctly beyond anterior crossvein ......... 6 
First vein ending at or near the level of anterior crossvein. 
Tephrochlamys (p. 516) 
. Three dorsocentral bristles. . . ... . . . .Heteromyza (p. 515) 
More than 3 dorsocentral bristles (in North orien fossils only have been 
TECOrGed)! F202 i= cfs . .. . . . Thelida (p. 516) 
. Five or more pairs of domocencral paitles: 3 Sain of scutellar bristles. 
Orbellia (p. 512) 
Four or fewer pairs of dorsocentral bristles; 2 pairs of scutellar bristles . . 8 
. Anterior crossvein at or before basal fourth of discal cell . Lutomyia (p. 530) 
Anterior crossvein near middle of discal cell or beyond. . ....... 9 
. Midtibiae without bristles except near apex . . . «op ee 
Midtibiae with several bristles along middle on antercdore! and postero- 
dorsal surfaces .. . ... . . . .Aecothea (p. 518) 
Midfemora with rows of bristles nteniosly . . . . .Eccoptomera (p. 522) 
Midfemora without rows of bristles anteriorly; Ta setae or hairs or 
irregularly placed bristles anteriorly ...... =O eee: 
Pteropleura with hairs or bristles . ........ iPseudolena (p. 533) 
Pteropleura bare. .. . RAIL ame > re ae Re D2 ot Lesa 
Mesopleura with hairs or bristles eS ARS to ame eae “Avionostanie (p. 541) 
Mesopleura bare... . SO ce, ce cep oun ats 3) Sepp ee 
Fronto-orbital bristles Banat in Teneen hae cee es a ee _Neolexia (p. 554) 
Anterior fronto-orbital bristle shorter than posterior bristle. . . ... .14 
Arista relatively short, less than 3 times the length of third antennal 
segment. 3 5. . 5S) tee RELL) 
Arista relatively fone pened iien 3 ames fhe > length ah third antennal 
segment. ..... 5. Sat LO 
Arista clearly pubescent; body sno welleg in newt North American 
species ... . . . . . . Spanoparea (p. 561) 
Arista bare or meaty SO; pede ioctl blacks in known North American species. 
Morpholeria (p. 564) 
One strong sternopleural bristle . . . ... .. . .Acantholeria (p. 565) 
Two (rarely 3) strong sternopleural bristles. . . . . Schroederella (p. 569) 
One (rarely 2 or 3) pairs of prosternal bristles; if more than 1 pair of prosternal 
bristles, then anterior fronto-orbital bristle shorter than posterior 
bristle? 73/7.) % cs! oF Yap pS 
Two or more pairs oF Seeer sl pewtless pee and meen fronto-orbital 
bristles about equal.in length = .'..22. © <<. ss obese eee 
