416 THE XOETH AMEBIC AN EMPIDJE—COQ UIL LETT. vol. xviii. 



81. Second joint of middle tarsi longer than the first one, each thicker than any 



of the others; length, 3 mm frontalis. 



Second joint shorter than the first ; neither of them thicker than those of the 



hind tarsi ; length, 5 mm irregularis. 



82. Femora and tibi;o destitute of erect scales 87 



Femora, or at least the under si<le of the hind ones, ciliate •with nearly erect 



scales 83 



83. Middle and hind femora bearing such scales 84 



Middle femora destitute of scales, antennal style one-sixth as long as the 



third joint ; length, 2| mm parva (p. 433). 



84. Length of body, under 6 mm 85 



Length, 9 mm.; scales of legs confined to under side of middle and hind 



femora; thorax subshiniug and marked "svith three deep black vittie; 

 California species fimhriata (p. 429). 



85. Middle and hind femora bearing scales on under side only 86 



Middle and hind femora ciliate on both sides, auteunal style one-fifth as long 



as the third joint; length, il mm ahdita (p. 430). 



86. Antennal style one-fourth as long as the third joint, tibial destitute of scales ; 



inhabits Colorado ; length, 4 mm effera (p. 427). 



Antennal style one-half as long as the third joint, hind tibite bearing nearly 



erect scales; California species; length, 5i mm stylala {Yt.io2). 



87. Palpi black 88 



Palpi yellow, thorax and abdomen ojiacxue, pile of abdomen yellowish ; 



length, 5 mm ; vara. 



88. Thorax opaque or nearly so 89 



Thorax shining, three vittaj and the sides white pollinose; abdomen shining, 



its pile yellowish ; length, 7 mm virgata (p. 430). 



89. Antennal style not over one-fifth as long as the third j oint 90 



Antennal style nearly one-half as long as the third joint; contact of discal 



and fourth posterior cells much shorter than that of the third and 

 foiirth posterior cells ; length, 6 mm flexuosa, (p. 433). 



90. Penultimate section of fifth rein much shorter than the ultimate section; 



front and middle metatarsi subequal in size, much smaller than the 



hind ones 91 



Penultimate section of fifth vein much longer than the ultimate section; 



length, 4i mm sordida. 



91. Thorax opaque, bluish gray pollinose, vein issuing from anal cell distinct, 



reaching the wing margin ; pile in front of halteres whitish; length, 



4 mm frontalis. 



Thorax opaque, gray pollinose, pile in front of halteres black; length, 3 mm. 



jiriajiiihis. 



Thorax subshining, lightly graj-ish-black pollinose, vein issuing from anal 



cell indistinct, not reaching the wing margin ; length, 3 mm cxigua. 



92. Males ; discal and posterior cells normal 93 



Females 102 



93. Eyes contiguous or nearly so ; length, 3 to 5 mm 94 



Eyes distinctly separated 100 



94. Filament of hypopygium not flexuous, sometimes hidden 95 



Filament tlexuous toward apex, not suddenly thickened at base; abdomen 



densely grayish- white pollinose; length, 3 mm nigricans. 



95. Posterior metatarsi never globose 96 



Posterior metatarsi very thick, globose, wings gray; length, 2i mm. .. impedita. 



96. Abdomen not grayish-white pollinose 97 



Abdomen opaque grayish-white pollinose; a long seta issuing from apes of 



lower lamella of hypopygium (not the usual central filament); Cali- 

 fornian species hifdata (p. 424). 



