Key to the females of Amazonian Leucotabanus species

1. All legs black. Subcallus smooth and shiny. Dorsum of abdomen completely black. Scutum and scutellum covered with lemonyellow hairs............................................................................... L. flavinotum

- At least the fore tibia bicolored, with white hairs in the proximal region. Subcallus pruinose. Scutum and scutellum otherwise................................................................................................... 2

2. Femora mostly with light hairs. Fore tibia not prominently bicolored............................................ 3

- Femora black or dark brown, with black hairs. All tibiae strongly bicolored, white in the proximal region, black distally... 4

3. Postpedicel black, as high as long, shorter than or subequal to length of style. Terminal abdominal segments not laterally compressed. Width of the frontal callus half the width of the frons....................................... L. weyrauchi

- Postpedicel orange, longer than high. Terminal segments of the abdomen compressed laterally. Width of the frontal callus no more than 1/3 of the width of the frons.......................................................... L. albovarius

4. Pterostigma pale yellow to inconspicuous. A brownish gray species. Frons narrow, frontal index greater than 6.0. Antenna orange to brown, style as long or smaller as postpedicel............................................... L. janinae

- Pterostigma brown to black, conspicuous. Blackish species. Frons variable. Antenna usually black, style as long or larger than postpedicel.......................................................................................... 5

5. Frons slender, frontal index 7.0 to 8.2, divergent above. Small species, wing size until 9mm. Wing very slightly smoky. Palpus with many white hairs. Terminal segments of the abdomen not compressed laterally....................... L. pauculus

- Frons parallel-sided and less slender, frontal index less than 6. Larger species, wing size usually greater than 10mm. Wing hyaline. Palpus and terminal segments of the abdomen variable................................................ 6

6. Palpus with black hairs. Terminal segments of the abdomen usually compressed laterally, pointed in dorsal view. Scutum evenly colored, dark.............................................................................. L. exaestuans

- Palpus with white hairs at least basally. Terminal segments of the abdomen not compressed laterally. Scutum with broad median spot of white hairs on the anterior half...................................................... L. fairchildi n. sp.