Couplet 1

Thorax mostly black haired; abdominal segments 2-6 with thick-set,

appressed straw-yellow hair, on segments 4-6 this yellow hair

sharply demarcated from lateral black hairs; mystax entirely black

in female. . . . .
semitecta (Coquillett)


Thorax always with preponderance of yellow and/or red (usually

yellow) hairs on mesonotum, especially on posterior portion;

abdominal segments variable, but never as described above; mystax

in female mostly yellow. . . . .
Go to Couplet 2

Couplet 2

Thoracic mesonotum with a band of red hair across posterior margin;

scutellum with red hair . . . . .
insignis (Banks)


Thoracic mesonotum with yellow hairs; scutellar hairs yellow or

black, never red. . . . .
Go to Couplet 3

Couplet 3

Abdominal tergite 6 black-haired in both sexes. . . . .
posticata posticata Say


Abdominal tergite 6 with yellow hairs in both sexes. . . . .
Go to Couplet 4

Couplet 4

Yellow hairs on posterior portion of mesonotum longer and more

thickly set than on anterior portion, giving dorsum of thorax a

definite "two-tone" look . . . . .
 
Go to Couplet 5


Yellow hairs on mesonotum uniformly distributed . . . . .
Go to Couplet 6
 

Couplet 5

Abdomen of male with most light hairs yellow, a few however forming

indistinct patches of washed-out red; first 3 abdominal tergites

black dorsally in female, contrasting sharply with the predominant

yellow on the more apical segments . . . . .
 
columbica Walker and partitor (Banks)


Abdomen of male and female with extensive red hairs; contrast in

female between black and lighter portions of abdomen not marked . . . . .
asturina (Bromley)

Couplet 6 (4)

Scutellar hairs yellow; mystax entirely yellow except possibly for a

few black hairs in lower third; palpal hairs yellow . . . . .
 
unicolor (Williston)


Scutellar hairs black; mystax with lower third entirely black; some

or all of palpal hairs black . . . . .
Go to Couplet 7

Couplet 7

First three and usually four abdominal tergites mostly or entirely

black haired, especially dorsally . . . . .
 
Go to Couplet 8


Abdominal segments 2-4 with extensive yellow and/or red hairs . . . . .
Go to Couplet 9

Couplet 8

Tuft of hair in front of wings and tuft in front of halteres yellow;

tibiae yellow haired . . . . .
 
astur Osten Sacken


Tuft of hairs in front of wings black, tuft in front of halteres

mostly or entirely black; tibiae black haired . . . . .
sackeni (Banks)

Couplet 9 (7)

Both sexes with yellow hairs on upper surface of posterior tibiae

extending to only slightly over half distance from base, forming

sharp contrast to black hairs on apical portion; hairs at sides of

first abdominal segment mostly black; red hairs at sides and

sometimes in middle of abdominal tergites 2-5 . . . . .
 
engelhardti (Bromley)


Both sexes with yellow hairs on upper surface of posterior tibiae

extending entirely to apex; hairs at sides of first abdominal

segment mostly yellow; red hairs at sides of abdominal tergite 3,

on most of 4, and in some specimens on middle of 5 . . . . .
fernaldi (Back)