Promachus is Greek for “fighter in the front ranks.” A fitting name for such a beast. These are typically large though often smaller than Proctacanthus.
Note the bi-colored legs (bright orange or reddish tibias with black femurs and tarsi) and banded abdomens. Black genitalia.
P. hinei is similar, but it has entirely reddish legs. It is not known from Florida, though it could occur in the western panhandle.
Habitat: These can be fairly common in deciduous woods, especially swamps and riparian areas.
Size: 28-35 mm
FL Range: Panhandle, north and central Florida south to Highlands County. Absent from south Florida.
FL Season: April – October
These grab your attention because they create a raucous buzz when they fly.
Promachus bastardii, which occurs across the eastern U.S. is very similar to P. quadratus, which is restricted to the southeast.
Abdomen brown-haired on sides and black above. Narrow band of white hairs on the abdominal segments, so there is more black shown on the thorax than in P. quadratus. Thorax brown. Bright white hairs covering male genitalia. Beard and mystax (face beard) yellow. Brown wings. Red legs with white hair and black bristles. Palpi black-haired. The white hairs against the dark abdomen, thorax, and legs makes these look distinctly purple to me in the field.
Size: 21-28 mm
FL Range: Throughout
FL Season: Late February – August
Very similar to P. bastardii. Bromley (1950) notes that “quadratus is larger that bastardii and with more white hairs on the body and legs”. One specimen Bromley examined was 41 mm in length. Mike Thomas examined specimens at FSCA and found the only difference is that P. quadratus has more white hairs on the body and legs (esp. pale hairs on mystax, beard, coxae and lateral margins of abdominal segments).
Martin (1965) notes: “The posterior margin of tergite 7 of quadratus is totally
black; dorsally tergite 4 has brown hair.”
Male genitalia shorter than abdominal segments six and seven combined, and it’s much longer in P. fitchii.
Size: ?-41 mm. Averages larger than P. bastardii.
FL Range: Supposedly throughout.
FL Season: April – July, though there is a February museum record from Dade County.
Male by Michael Thomas which shows extensive white hairs on the rear of the thorax
Promachus texanus confusion
Brad Moon posted a fantastic series illustrating the differences between P. bastardii and what he is calling P. quadratus here. Brad is likely showing an excellent comparison of P. bastardii and P. texanus.
Mike Thomas suggested that Hine (1911) incorrectly described P. texanus as P. quadratus. His analysis is as follows:
Bromley’s description of P. texanus is: yellowish brown and pollinose species, wings very pale brown, abdomen black, yellow pilose, third abdominal segment usually with short black hairs anteriorly and laterally, gray shadow in the first submarginal cell narrower that the marginal cell. Bromley deposited 45 specimens of texanus (both sexes) at the Tex Ag. Exp. Station & Tex. A. & M. college, so it must have been a fairly common species not far from Houston (College Station). Bromley states that “P. texanus has been frequently identified as P. quadratus, a large form related to bastardii occurring in the southeastern states”. Perhaps he was referring to Hine’s specimens or others from the vic. of Cameron Parish.
Overall yellowish-tan colored compared to dark brown on P. bastardii. Abdomen yellowish-gray haired on sides. Wide band of pale-yellowish or white hairs on each abdominal segment such that there is less black showing than in P. bastardii. Beard and mystax yellow. Wings pale yellowish. Palpi yellow-haired with a few black hairs intermixed. Long hairs on back of thorax yellowish with a few black bristles, as opposed to entirely black in P. bastardii. P. bastardii also has wider gray shading in the first submarginal cell of the wings than P. texanus, but this is difficult to see. Shorter male genitalia than P. bastardii.
Range: Texas, Oklahoma, Mexico, and apparently Cameron Parish, Louisiana.
Note the white-haired genitalia are longer than segments five, six, and seven combined. The eyes are often a red, green, or both. Yellow-haired overall.
Typically found in tall-grass prairie.
Size: 25-30 mm
FL Range: There is a museum specimen marked as Florida, though I’m unsure if it’s correct. Hine (1919) also mentions a Florida record.
Bromley, S. W. (1934). The robber flies of Texas (Diptera, Asilidae). Annals of the Entomological Society of America, 27(1), 74-113.
Bromley, S. W. (1950). Florida Asilidae (Diptera) with description of one new species. Annals of the Entomological Society of America, 43(2), 227-239.
Martin, C. H. (1965). Generic and subfamily changes, new synonymy, new names, a new species, and notes on Asilidae (Diptera). Journal of the Kansas Entomological Society, 110-134.
Hine J.S. (1911) Robberflies of the genera Promachus and Proctacanthus. Ann. Ent. Soc. Amer. 4(2): 153-172