Couplet 1

Ground color of femora orange; medium sized to large (16-25 mm long)

wasp-like fly restricted to Coastal Plain . . . . .
saffrana Fabricius


Ground color of femora dark reddish brown to blue black; bumble-bee

like flies of variable size and geographic distribution . . . . .
Go to Couplet 2

Couplet 2

Hair in front of wings, halteres, and on scutellum all yellow;

upper portion of mystax black or mostly so (a few yellow hairs

may be present centrally) . . . . .
Go to Couplet 3


Hair in front of wings and/or in front of halteres and/or on

scutellum black; upper portion of mystax variable . . . . .
Go to Couplet 4

Couplet 3

Posterior surface of fore-tibiae, and anterior, dorsal, and

posterior surfaces of mid-tibiae covered with extremely conspicuous

long, bright yellow hairs; mesal third of posterior surfaces of

hind tibiae each with a patch of sparse yellow hair, which is most

distinct when viewed from above level of fly (i.e. looking "down"

the tibiae from its base); first abdominal tergite covered with

yellow hairs, except along extreme lateral margins, where some hairs

are black; tergites 2-3 haired similarly; remaining tergites black

haired; this fly is very similar to some individuals of the extremely

variable L. thoracica, but can be readily recognized by its smaller

size (15-20 mm long), more slender build, and invariable abdominal

coloring; found from Wisconsin to Quebec and south to Connecticut

. . . . .
sacrator Walker


Fore- and mid-tibiae with some yellow hair, but this hair is never

conspicuous; mesal third of posterior surfaces of hind tibiae

entirely black haired; first abdominal tergite entirely black

haired; hairing of tergites 2-3 extremely variable, from nearly

all yellow to entirely black; abdomen often entirely black; this

fly is in general larger (15-25 mm) and more stockily built than

the similar L. sacrator, and is probabily the most convincing

bumble-bee mimic in the entire genus; found throughout most of the

eastern United States . . . . . .
thoracica Fabricius

Couplet 4 (2)

Abdominal tergite 1 with yellow hairs laterally, black hairs

medially; tergites 2-7 entirely black haired; scutellar hairs

long and abundant on both disk and margin, bright yellow; small

to medium-sized (11-20 mm) fly found throughout most of eastern

United States . . . . .
flavicollis Say


Abdominal tergite 1 either lacking yellow hairs laterally, and/or

tergites 2-7 with yellow hairs present; scutellar hairs variable;

body size and geographic distribution variable . . . . .
Go to Couplet 5

Couplet 5

Abdominal tergites covered with layer of black hair; yellow hairs

lacking; scutellar hairs black . . . . .
Go to Couplet 6


Abdominal tergites with prominent areas of hairless cuticle and/or

with yellow hairs present; scutellar hairs variable . . . . .
Go to Couplet 7

Couplet 6

Mesonotum with pile appearing olive yellow from a distance; hind

femora each with a thick flange of bright yellow hairs stretching

dorsally from near base to about three-fourths way to apex; tufts

of hair in front of halteres entirely black; medium-sized (15-24 mm)

fly found along Atlantic seaboard from Cape Cod to Florida . . . . .
affinis Macquart


Mesonotum with pile appearing bright yellow from a distance; hind

femora entirely black haired; tufts of hair in front of halteres

mostly yellow; slightly smaller (13-20 mm) fly found throughout

most of the southeastern United States . . . . .
virginica (Banks)

Couplet 7 (5)

Mystax entirely black, except possibly for a few adventitous

yellow hairs dorsally in male; hairs in front of wings, in front

of halteres, and on scutellum all black; medium-sized to large flies

(19-27 mm) found in Texas. . . . .
Go to Couplet 8


Mystax yellow on upper portion of facial gibbosity, black on sides

of oral cavity or lower portion: hair in front of wings, in front

of halteres, and on scutellum variable; size and geographic

distribution variable . . . . .
Go to Couplet 9

Couplet 8

Male with about apical posterior third of each fore-tibia, and

entire length of dorsal half of each mid-tibia, with extremely

conspicuous yellow hairs; female similar, except that fore-tibiae

are entirely black-haired; abdominal tergite 1 with substantial

amount of yellow hair in both sexes; large (22-27 mm long) fly

. . . . .
macquarti (Banks)


Male with fore-tibiae, mid-tibiae, and abdominal tergite 1 entirely

black haired; female unknown, but likely to be similar; slightly

smaller (19 mm long) fly . . . . .
nigella (Bromley)

Couplet 9 (7)

Thoracic mesonotum with a band of red hair across posterior

margin; scutellum with red hair; small (13-18 mm long) fly found

from Michigan, across Ontario and Quebec to Labrador . . . . .
insignis (Banks)


Thoracic mesonotum and scutellum variable, but lacking red

hair; size and geographic distribution variable . . . . .
Go to Couplet 10

Couplet 10

Hairs on margin of scutellum entirely yellow, always long and

conspicuous . . . . .
Go to Couplet 11


Hairs on margin of scutellum all or mostly black, and sometimes

short and inconspicuous . . . . .
Go to Couplet 13

Couplet 11

Back of head with at least some black hairs fringing outside upper

margin of eye; these hairs may be very inconspicuous; hind tibiae

with only black hairs dorsally . . . . .
Go to Couplet 12


Yellow hairs fringing eyes around entire outside margins; hind

tibiae with many golden-yellow hairs dorsally; medium-sized

(15-18 mm), stocky fly found from Michigan to Ontario . . . . . 
posticata scutellaris (Bromley)

Couplet 12

Many black hairs on back of head and fronting upper third of margin

of eye; hairs on disk of scutellum conspicuous and yellow; abdominal

tergite 3 entirely with black hair; small to medium-sized (11-18 mm

long) fly found in northeastern United States . . . . .
divisor (Banks)


Back of head with just a few black hairs fronting upper fourth of

margin of eye; hairs on disk of scutellum inconspicuous and black;

abdominal tergite 3 with patches of yellow hairs to each side along

posterior margin; small (10-15 mm long) fly found in Michigan . . . . .
royalensis (Bromley)

Couplet 13 (10)

Visible dorsum of all abdominal tergites except 5 entirely bare,

showing a ground color of polished black; some hairs present along

extreme lateral margins of all tergites; in the male all of these

lateral hairs are black; in the female some of the hairs on tergites

1-2 are yellow;  in both sexes dorsum of tergite 5 similar to that

of the other segments, except that the lateral hairs extend slightly

further medially, and in the female form conspicuous yellow patches;

very large to huge (28-35 mm long) fly from Florida . . . . .
apila (Bromley)


Dorsum of at least some abdominal tergites with abundant hairs

medially; size and geographic distribution variable . . . .
Go to Couplet 14

Couplet 14

Tufts of hair in front of wings entirely pale . . . . .
Go to Couplet 15


Tufts of hair in front of wings mostly or entirely black . . . . .
Go to Couplet 18

Couplet 15

Hind femora each with a thick flange of pale hairs stretching

dorsally from near base to about three-quarters way to apex; apex

or "knee" with conspicuous tuft of pale hairs; all pale hairs on fly

very light yellow, almost dirty white; small (10-16 mm long),

lightly built fly found in northeastern United States. . . . .
cinerea (Back)


Hind femora black haired, except possibly for a few inconspicuous

pale hairs on apex or "knee;" all pale hairs on fly bright yellow;

larger (19-24 mm long), stockier flies; geographic distribution

variable . . . . .
Go to Couplet 16

Couplet 16

Abdominal tergite 6 covered with red hair; described from single

large (26 mm long) female taken at Yonah Mountain, Georgia . . . . .
fattigi (Bromley)


Abdominal tergite 6 black-haired; slightly smaller (19-24 mm long)

fly; geographic distribution variable . . . . .
Go to Couplet 17

Couplet 17

Abdominal tergite 5 with black hair medially and posteriorly:

apices or "knees" of hind femora entirely black haired; stocky,

medium-sized to large (19-24 mm long) fly found in northeastern

United States . . . . .
champlainii (Walton)


Abdominal tergite 5 entirely covered with yellow hair; apices

or "knees" of hind femora with a few, scattered very inconspicuous

yellow hairs, which cannot be seen without using a dissecting

microscope at over 40X ; stocky, medium-sized (20 mm long) fly

found in eastern portions of Kansas and Nebraska   . . . . .
vorax (Bromley)

Couplet 18 (14)

Abdominal tergite 1 entirely black haired . . . . .
Go to Couplet 19


Abdominal tergite 1 with substantial amount of yellow hair . . . . .
Go to Couplet 21

Couplet 19

Abdominal tergite 3 with black hairs medially; yellow hairs

restricted to dorsolateral patches along posterior margin; male

with posterior margin of basistylus smoothly curved; small to

medium sized (12-18 mm long) fly; found in northeastern United

States . . . . .
posticata posticata Say


Abdominal tergite 3 with yellow hairs medially; these hairs may

be partially rubbed off in some older males; male with posterior

margin of basistylus irregular or "notched;" large to huge

(23-39 mm long) fly; geographic distribution variable . . . . .
Go to Couplet 20

Couplet 20

Light hairs bright to dull yellow ; tufts of hair in front of

halteres entirely dull yellow; large to huge (23-35 mm long)

fly found from New England to South Carolina, with stragglers

into Florida . . . . .
grossa (Fabricius)


Light hairs very dirty yellow to brownish yellow; tufts of hair

in front of halteres with some black; very large to huge

(27-39 mm long) fly apparently restricted to the western portion of

the lower Mississippi Valley, from easten Texas and southeastern

Kansas, east to Missouri . . . . .
lata Macquart

Couplet 21 (18)

Hind femora each with a dorsal flange of long yellow hairs, reaching

from near base to about three-fourths way to apex; apices or "knees"

entirely black haired; abdominal tergite 4 with yellow hairs

restricted to thin band along anterior margin; a moderately large

(22-27 mm long) fly restricted to Florida . . . . .
floridensis (Bromley)


Hind femora with black hairs dorsally; apices or "knees" with

a few, scattered very inconspicuous yellow hairs, which cannot

be seen without using a dissecting microscope at over 40X;

abdominal tergite 4 covered with yellow hair, except for a few

black hairs and bristles at the extreme lateral margins; a

medium-sized (15-20 mm long) fly found from the Lake states to

Vermont and North into southern Canada . . . . .
huron (Bromley)