Ommatius

These small, hump-backed flies are often found in deep shade. The genus is unique in having feathered antennae. There are four species recorded in Florida. However, O. floridensis was first described in 1984 and is very similar to O. tibialis. I suspect most museum records for O. tibialis in Florida are actually O. floridensis, and O. tibialis is restricted to the panhandle “highlands” such as Torreya State Park.

Ommatius wilcoxi

Let’s start off with the easy one. O. wilcoxi has dark reddish-yellow legs (femora and tibias) and dusky wings. Black on the femora is restricted to the tips.

Size: 13-17 mm

Season: May – September

FL Range: Panhandle and north Florida south to Gainesville

Male
Female
The male genitalia has a pointed epandrium (upper genitalia) and a bump on the hypandrium (lower genitalia).

Ommatius gemma

The legs are pale yellowish, transitioning to black. The rear femora are about one-third black. The presence of two long bristles on the rear of the scutellum (bump above the wings), differentiated from any other hairs on the scutellum, is distinctive in O. gemma. Also note the small size. When viewed laterally, the epandrium (upper male genitalia) has a very thin projection, making it appear strongly pointed. The hypandrium (bottom of male genitalia) is rounded.

The ventral margin of female abdominal segment 8 is broadly rounded and has a short point in the middle. This can only be seen on a specimen.

Size: Small. 9-13 mm

Season: February – December

FL Range: Throughout

Male
Note the vertical bristles on the rear of the scutellum (bump above the wings)
Female
Female
Female
The vertical bristles can be difficult to see, though they are apparent on the third photo here.
Male genitalia with very thin upper projection on epandrium, making it appear strongly pointed.

Ommatius floridensis

Both O. floridensis and O. tibialis have orange and black legs. The shape of the end of the male genitalia (epandrium) separates O. floridensis from O. tibialis. When viewed laterally, the epandrium (upper male genitalia) has a more pointed projection on O. floridensis; it’s more rounded in O. tibialis. The hypandrium (bottom of male genitalia) has a knob, which is lacking in O. tibialis. Both O. floridensis and O. tibialis have no clearly differentiated vertical bristles on the scutellum (bump above the wings) like O. gemma has.

The W- or U-shape of the posterior ventral margin of abdominal segment 8 is important in the females. It’s a shallow W in O. floridensis and a deeper W in O. tibialis. You need a specimen to see this, though I would be keen to see if anyone can get an in-situ macro shot of the underside of one.

Size: 14-16 mm

Season: March – December

FL Range: Throughout

Male
Male
Female
Male genitalia with strongly pointed epandrium (upper part) and pronounced bump on the hypandrium (lower part).

Ommatius tibialis

When viewed laterally, the hypandrium (bottom of male genitalia) has no knob like O. floridensis. Legs are orange and black, possibly with more black on femurs on average than on O. floridensis. No long bristles on scutellum (bump above wings).

Size: 13-16 mm

Season: June – September throughout eastern range

FL Season: June

FL Range: Panhandle. Bullington and Lavigne (1984) lists one Florida record from Liberty County, likely the June specimen from Torreya State Park at FSCA.

Male
Female

Diagrams from Bullington & Lavigne (1984)

O. tibialis
O. floridensis
O. wilcoxi
O. gemma
Lateral view of male genitalia, which show the differences in the shape of the epandrium (ep) and hypandrium (hp). Diagrams from Bullington & Lavigne (1984), included for nonprofit educational purposes.

References:

Bullington, S. W., & Lavigne, R. J. (1984). Review of the genus Ommatius Wiedemann (Diptera: Asilidae) in eastern United States with descriptions of five new species. Annals of the Entomological Society of America, 77(4), 372-392.

Scarbrough, A. G. (2008). New Ommatius Wiedemann from the Americas with two new species groups, keys, and taxonomic notes (Diptera: Asilidae). Insecta Mundi, 151.

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