Key to the known species of Heissothignus *

1. Humeral pronotal angles produced into sharp acute projections........................ H. armatus Slater & Brailovsky

- Humeral angles of pronotum evenly rounded, lacking acute projections........................................... 2

2. Pronotal coloration uniformly yellowish brown..................................... H. perfectus Slater & Brailovsky

- Pronotal coloration non-uniformly yellowish brown.......................................................... 3

3. Pronotum with dark reddish brown central band with lateral areas strongly contrastingly pale yellow............................................................................................... H. reclusus Slater & Brailovsky

- Pronotum with another pattern of color.................................................................... 4

4. Antenniferous tubercle clearly extending forward over base of antennae with apex curved around base of antennal segment I; anterolateral margin of anterior pronotal lobe narrowly carinate; posterior angle of connexival segments II to VI tiny exposed;

spiracles of abdominal sterna III and IV directly on lateral edge................................... H. slateri sp. nov. - Antenniferous tubercle scarcely attaining the base of antennal segment I, with apex rounded and not curved; anterolateral margin of anterior pronotal lobe remarkably carinate; posterior angle of connexival segments II to VI projected as short acute spine; spiracles of abdominal sterna III and IV far from lateral edge of abdomen..................... H. baitetus sp. nov.