Lampria bicolor
Entirely black legs. Bromley (1950) indicates these are found on or near oak stumps or logs. Bedell (2010) has found these in deciduous woods and woodland edge habitats.
Range: Eastern U.S. and Canada
FL Range: South to Highlands County
FL Season: March-October
Lampria rubriventris
Golden pruinosity on the scutum. Reddish tibiae. Bromley (1950) indicates these are found in moist fields.
Range: Eastern U.S. west to Wyoming and Colorado, south to Mexico.
FL Range: South to Highlands County
FL Season: May-September
References:
Bedell, P. (2010). A preliminary list of the robber flies (Diptera: Asilidae) of Virginia. Banisteria, 36, 3-19.
Bromley, S. W. (1950). Florida Asilidae (Diptera) with description of one new species. Annals of the Entomological Society of America, 43(2), 227-239.
Robber Flies of Florida 