Diogmites (Hanging Thieves) are charismatic predators, often hanging by one or two legs while they consume their prey. They are common throughout the state, but they can difficult to identify.
The available keys focus on the dark markings on the scutum (aka mesonotum or the top disc of the thorax), but there are other characters to check such as overall size, the shape of the abdomen, and markings on the side of the abdomen. Some species are variable.
Below are the species known or thought to occur in Florida.
Visual index of scutums
Note whether the middle stripe is undivided (neoternatus, ternatus, misellus, some properans), whether it reaches the pronotum (near head) or not, stripe thickness and color, and disc color. The stripes on the abdomen also can be helpful. See species accounts below for more detail.
Diogmites neoternatus
The most common species throughout most of the eastern United States is D. neoternatus. Thankfully this one is relatively easy to ID. The abdomen is orange and unmarked, and the top of the abdomen is pinched. Additionally, the stripes on the scutum are dark black, and the central stripe is undivided. The central stripe fades to red toward the pronotum (top of the thorax near the head) and rarely, but sometimes reaches the pronotum.
This is the only species in the area with an unmarked abdomen, and only D. neoternatus and D. ternatus have pinched abdomens.
Size: 20-30 (average 23.9) mm
Range: Throughout eastern U.S.
FL Range: Throughout
FL Season: late April-November
Diogmites ternatus
This is supposed to be similar to D. neoternatus, but the central stripe on the scutum usually reaches the pronotum (top of thorax near the head), is undivided, and is entirely black. The anterior of the central stripe is black and does not shade to red or brown. Based on FSCA specimens, it appears the lateral stripes are thick and undivided or nearly undivided. The lateral stripes are typically divided in D. neoternatus. Both D. neoternatus and D. ternatus have a pinched abdomen. D. ternatus is “rather small,” and most specimens should be smaller than D. neoternatus, which varies from 20-30 (average 23.9) mm. Bromley (1931) indicated the pollen on on the thorax of D. ternatus was more golden, and that D. ternatus has a blackish area above the second and third coxae, but neither of these traits is apparent on specimens.
There are numerous specimens at FSCA. I’m not convinced this species is valid – they could be small, well-marked D. neoternatus. Or perhaps more appropriately, D. neoternatus should be lumped back with D. ternatus, which was described first.
Size: 16-23 (average 21.0) mm
Range: Cuba, though there are records as far west as Texas and Kansas (Artigas, 1966).
FL Range: Possibly throughout. Artigas (1966) lists a specimen from Jacksonville, and FSCA has specimens from Alachua and Marion counties. One photo below is from Seminole County.
Diogmites crudelis
While variable in size, some individuals approach the largest robber flies we have at 48 mm. If you see a Diogmites and are struck by how massive it is, it’s probably D. crudelis. In this distinctive species, the stripes on the scutum are brown (not black), though they sometimes have narrow brown lines within them. The abdomen has “dark dorsal bands that are more or less interrupted mesally, lateroposterior angles of tergites golden.” (Artigas, 1966). Male genitalia yellow-haired.
Size: Huge, 26-48 (average 32.3) mm
Range: Southeastern US (NC, SC, GA, FL, AL, MS)
FL Range: Throughout
FL Season: May-October
Brad Moon’s photo series of D. crudelis from Louisiana is also helpful.
Diogmites salutans
Of all of the Florida species, this one may be the most tricky. The stripes on the thorax are brown (not black) and are “not strongly contrasting with color of disc.” The central stripe on the thorax is narrowly divided for its entire length. There is a black band on each abdominal segment. These are smaller than D. crudelis. Male genitalia black-haired.
Size: 20-25 (average 21.7) mm
Range: VA to FL, west to OK, AR, MS
FL Range: South to Manatee, Highlands, and northern Palm Beach Counties
FL Season: April-October
On this photo of a male D. salutans, you can clearly see the black hairs on the genitalia.
Diogmites properans
Central stripe on scutum is usually undivided and reaches the pronotum (front of thorax near the head). The markings on the thorax are velvety black, whereas they are brown on D. salutans. Black dorsal bands on abdomen, with “band sometimes becoming brownish or reddish mesally” (Artigas, 1966).
Size: 15-28 (average, 22.0) mm
FL Range: Most common in the panhandle with a few north Florida records. There are museum specimens recorded south to Manatee County, but many of these may be misidentified.
FL Season: May-September
Diogmites esuriens
Central stripe on scutum is divided and does not reach the pronotum (front of thorax near the head). Markings on thorax black, contrasting strongly with the pale disc color. Abdomen has slight constriction between second and third segments. Abdomen “tergites usually with a black oblique line on proximal angle, contrasting with the brown or golden background color, the posterior angles of tergites golden pruinose” (Artigas, 1966).
Size: 21-31 (average 25.0) mm
FL Range: Throughout
FL Season: late April-November
Diogmites misellus
Central stripe on scutum is undivided for most of its length, but it does not reach the pronotum (front of throax near the head) and shades to red toward the head. Markings on thorax are black. No black markings on abdomen but still has darkened segments so appears banded unlike D. neoternatus. Most specimens have a more distinct black mark at the distal end of the rear femora compared to D. neoternatus.
Size: Smallest Diogmites in the genus, 16-23 (average 19.2) mm
Range: Eastern U.S.
FL Range: Panhandle and north Florida south to Alachua County
FL Season: June-August
Diogmites discolor
Dark scutum (top of thorax) with black stripes, including a divided central stripe. Abdomen dark with silver spots on side of tergites (abdominal segments). Dark eyes.
Size: 19-31 (average 24.0) mm
Range: Eastern U.S.
FL Range: It may occur in the western panhandle
Season: June-September throughout range
Diogmites platypterus
Dark overall including top and sizes of thorax and abdomen with dark wings. Legs orange. Dark eyes.
Size: 20.5-28.0 (average, 23.6) mm
Range: Midwest and eastern U.S.
FL Range: There is one October record from central Florida (Lake Alfred in Polk County) and one published record from Gainesville. It may occur in the western panhandle.
Season: May-early November throughout range
Diogmites angustipennis
This species has not been recorded in Florida. It can only be distinguished from D. bilobatus via dissection. However, Barnes (2010) found that D. bilobatus has been recorded from California east to Louisiana, but D. angustipennis has several Mississippi and Alabama records. So D. angustipennis is more likely to turn up in the Florida panhandle. The markings and size vary widely, but both D. angustipennis and bilobatus lack distinct dark markings on the brown scutum (top of thorax). Check out the reddish hues to the eyes.
Size: Varies widely. Male 16.5–28.9 mm (mean = 23.4 mm); female 15.2–29.9 mm (mean = 24.2 mm).
Season: April to late November throughout its range, though most specimens are July to September
References:
Artigas, J. (1960). The Genus Diogmites in Eastern North America (Diptera: Asilidae) (Doctoral dissertation, The Ohio State University).
Artigas, J. N. (1966). The Genus Diogmites (Robber Flies) in Eastern United States (Diptera: Asilidae). Ohio J. Sci. 66(4): 401-421.
Barnes, J. K. (2010). Nearctic species related to Diogmites angustipennis Loew (Diptera: Asilidae). Zootaxa, 2545(1), 1-22.
Bromley, S. W. (1931). New Asilidae, with a revised key to the genus Stenopogon Loew:(Diptera). Annals of the Entomological Society of America, 24(2), 427-435.
Dennis, D. S. (2015). Ethology of Diogmites crudelis Bromley, 1936 (Diptera: Asilidae) in Northeastern Florida, USA. Journal of the Entomological Research Society, 17(1), 23-44.
Robber Flies of Florida 