If you thought Efferia were tricky, prepare to be demoralized by Machimus. Machimus are similar to Efferia, though they are browner and do not have the swollen male genitalia nor swordlike ovipositors. Also compare other genera in the Asilinae subfamly: Neoitamus, Philonicus, and Polacantha.

Machimus are very difficult to ID. The coloration on the femurs and tibias and the leg hair color are important. Seasonality is also important, with most species either having a spring or fall flight season. Greatest diversity is in the panhandle and north Florida. Only the range of M. floridensis and hubbelli includes south Florida, and both of those are Florida endemics.

The best way to distinguish males of several Machimus species is by genital shape, especially that of the proctiger, a structure between the epandrium halves. Specimens are needed to see this. I have organized the species accounts below based on femur color. Note there is a difference between an entirely black femur and a black femur with a small red tip. Though there are exceptions, the color of the femora, tibiae, metatarsi, leg hairs, and mystax (face beard) can usually get you most of the way toward an ID.

Mostly red femora

SpeciesSizeMystaxFemurTibiaMetatarsiLeg hair
fattigi23-26 mmwhitishMostly red with minor black spotsredredbristles black
polyphemi11-18 mmgolden yellowReddish yellow with black in middle portion of anterior surfacesreddish yellow basallyreddish yellow with black tips 

Machimus fattigi

Red femora, tibiae, and metatarsi. White mystax (face beard).

Size: Large. 23 to 26 mm

FL Season: May – June

FL Range: Panhandle

Machimus polyphemi

This species is found either within or very close to gopher tortoise burrows. Bullington & Beck (1991) hypothesized that this species (and two western sister species which occur in Badger burrows) retreated to burrows to find a favorable microclimate as the climate changed. Once they became completely adapted to burrows, they may have been able to fully realize this niche and spread to a larger geographic area than their original distribution. A great writeup on survey methods for this species can be found here.

A very golden yellow species overall, with extensive reddish on femora and tibiae. Golden yellow mystax.

Size: 11-18 mm

FL Season: May to July

Range: MS, GA, FL

FL Range: Recorded in panhandle and north Florida (Santa Rosa, Putnam Counties in Bullington & Beck, 1991; and Alachua, Hamilton, Gadsden, and Liberty counties based on an ongoing survey led by Jonathan Mays). It may occur throughout the state where there are Gopher Tortoises.

Black femora and tibiae

SpeciesSizeMystaxFemurTibiaeMetatarsiLeg hair
maneei10-12 mmgray and black hairsShining blackblack, sometimes with trace of reddish at base of tibia femora with some white hair and black bristles

Machimus maneei

Mostly-black, entirely black legs. There can be a trace of red at the base of each tibia in some specimens, and there can be reddish hairs on the inside of the rear tibiae and tarsi.

Size: Small. 10-12 mm

Season: April – November throughout range. Dirk Stephenson has found these are downright common in October and November in good habitat in Georgia. There is a Florida October record at FSCA.

Range: Eastern U.S. and Canada, north to Ontario, west to Illinois and Arkansas.

FL Range: Gainesville

Habitat: Turkey oak sandhills and likely other sandy pinewoods.

Excellent photo of a male by Brad Moon.

Brown femora and tibiae

SpeciesSizeMystaxFemurTibiaeMetatarsiLeg hair
hubbelli11-15 mmwhite with some black bristlesBrown, though black on anterior aspectsBrown to black Black bristles, white hairs

Machimus hubbelli

Similar to M. maneei, but legs and hypopygium brown instead of black.

Size: 11-15 mm

FL Season: September – December

FL Range: Clay County to Highlands County. Florida endemic.

Entirely black femora

SpeciesSizeMystaxFemurTibiaeMetatarsiLeg hair
frosti12-14 mmblack above, pale belowblackred with black tips underside of front femora with long fine pile as in M. snowii. black bristles and pale hairs
notatus14-18 mmdarkblackred on basal third
novaescotiae14-18 mmblack above, yellowish below. Sometimes entirely light.blackyellow with black tipsmostly yellow
sadyates13-17 mmdark upper mystaxblackone side black, one side yellowish or reddish

Machimus frosti

Entirely black femora, mostly red tibiae, mystax black above and pale below, found in Spring. Underside of front femora with long hairs. Wingtips pale brown. Third antennae segment narrow and same length as arista (antennae tip). Male genitalia similar in form to M. virginicus.

Size: 12-14 mm

FL Season: March – May

FL Range: North and Central Florida

Machimus notatus

Black femora, and mostly black tibiae with red only on the basal third. Dark mystax and face.

Size: 14-18 mm

FL Season: April, May, July

FL Range: Gainesville and Jackson County (panhandle)

Machimus novaescotiae

All black femora. Tibiae yellow (or orange) with black tips. Metatarsi mostly yellow. Mystax black above, yellowish below. Somestimes the mystax is entirely light-colored. Occipital bristles mostly black above and yellowish at sides. Penultimate abdominal tergite on the female tomentose. Third antennae segment narrow and same length as arista (antennae tip). Male forceps (on genitalia) supposedly as long as abdominal segments 6-8.

Size: 14-18 mm

FL Season: April – May

FL Range: Panhandle and North Florida

Machimus sadyates

All black femora. Dark legged. Dark upper mystax. Penultimate abdominal tergite on the female shiny black. Note that one side of each tibia is yellowish or reddish, and one side is black.

Size: 13-17 mm

Season: July – November

FL Range: There are Citrus and Hillsborough County records in the FSCA collection, though these are likely erroneous, especially since one is marked as March. This species likely does not occur in Florida. It’s predominantly a northeastern species.

Dark femora with reddish tip

SpeciesSizeMystaxFemurTibiaeMetatarsiLeg hair
blantoni16-21 mmpale with some black hairsdark with reddish tipreddish, extreme tips blackreddish with black tipslong fine white pile under front two femora. Bristles black.
erythocnemius11-14 mmwhite or yellowish with a few short black ones abovedark with reddish tip. Prominent orange femur with black apex, usually with dark marking near the middle of the anterior sideredventral profemur bristles weak and white, but lacking the fine white hairs on femur as in M. snowii. White bristles posteriorly on the protibia.
floridensis14-15 mmstraw yellow, upper part with black bristlesBlackish except for distal fifth to third of the posterior aspects, which are reddish.reddish with black tips, black spot on middle of the inner sidereddish with black tipsblack bristles, underside of front femora with white hairs (based on limited observations)
lecythus18-21 mmblack above and yellowish belowblack with red tipsyellow with black tipsyellow 
paropus13-17 mmyellowish with few black hairsdark with reddish tipdark with yellowish tipdark with yellowish tipVentral profemur bristles stout and black.
snowii15-20 mmmostly blackdark with reddish tipmostly orange. Front and middle tibiae with a ring near the middle and the apex black. underside of front femora with long fine hairs

Machimus blantoni

Gray overall with deep red tibiae and tips of femora. Pale mystax with some black hairs. Long fine white pile under the two front femora is distinctive for this species. Leg bristles black. Blunt/rounded tip of male genitalia.

Similar species: Machimus snowii has long white hairs under the front femora only, the color on the tibiae and femora is more orange, and M. snowii has a dark ring near the middle of the front two tibiae. M. snowii also has more pointed male genitalia.

Size: 16-21 mm

FL Season: March – May

FL Range: Panhandle (Escambia, Santa Rosa, Okaloosa, and Walton Counties), also one location in southeastern Georgia

Machimus erythocnemius

Golden-faced. Mostly white or yellowish mystax. Dark femur with reddish tip, prominent orange femur rings, ventral profemur bristles weak and white, but lacking the fine white hairs on femur as in M. snowii. White bristles posteriorly on the protibiae.

Size: 11-14 mm

Season: July – August in northeastern US

Hine (1909) indicated a record from Punta Gorda in November, which was likely M. floridensis which had not yet been described. Likely erroneous in Florida.

Machimus floridensis

Straw yellow mystax with some black bristles above. Femora blackish except for distal fifth to third of the posterior aspects, which are reddish. Tibiae reddish with black tips, black spot on middle of the inner side. This makes the legs look mottled. Wings are reddish and subhyaline. Occipital bristles are black.

Size: 14-15 mm

FL Season: August – November. One April record.

FL Range: Peninsula

Male found by Chris Rorabaugh in Orange County

Habitat in Bradford County, FL: grassy trail next to wet myrtle swamp and pine flatwoods. Habitat preference seem to be in clearings or wet forest edges.

Machimus lecythus

Femora black with red tips. Mainly yellow tibiae. Occipital hairs black and yellowish.

Size: 18-21 mm

Season: May – June in GA. Unsure if occurs in Florida.

Habitat: “rank riparian vegetation or unmowed grasslands” (Bedell, 2010)

Machimus paropus

Yellowish mystax. Dark femur with reddish tip. Dark tibia with yellowish tip. Ventral profemur bristles stout and black. Occipital hairs yellow, but this trait varies.

Size: 13-17 mm

FL Season: June

FL Range: Gainesville record. May be erroneous in Florida.

Machimus snowii

Mostly black mystax. Dark femur with reddish tip. Underside of front femora with long fine hairs. Mostly orange tibiae. Front and middle tibiae with a ring near the middle, and the apex black.

Size: 15-20 mm

Season: June – September in eastern U.S. and Canada

FL Season: April

FL Range: Panhandle

Published diagrams of male genitalia from Hine (1909), Bromley (1940), and Baker (1970)


Baker, N. T. (1970). A taxonomic and ecologic study of the asilidae of Michigan (Doctoral dissertation, Michigan State University. Department of Entomology).

Bedell, P. (2010). A preliminary list of the robber flies (Diptera: Asilidae) of Virginia. Banisteria, 36, 3-19.

Bromley, S.W. (1940). New U.S.A. robber flies (Diptera: Asilidae). Bulletin of the Brooklyn Entomological Society 35(1): 13-21.

Bromley, S. W. (1950a). Florida Asilidae (Diptera) with description of one new species. Annals of the Entomological Society of America, 43(2), 227-239.

Bromley, S. W. (1950b). Records and descriptions of Asilidae in the collection of the University of Michigan Museum of Zoology (Diptera).

Bullington, S. W., & Beck, A. F. (1991). A new species of Machimus Loew (Diptera: Asilidae) from burrows of Gopherus polyphemus (Testudines: Testudinidae). Annals of the Entomological Society of America, 84(6), 590-595.

Hine, J. S. (1909). Robberflies of the genus Asilus. Annals of the Entomological Society of America, 2(2), 136-170.

McAtee, W. L., & Banks, N. (1920). District of Columbia Diptera: Asilidae. Proceedings of the Entomological Society of Washington, 22(1), 21-33.

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