Key to the known species of Bianigryllacris

1 Frons with broad transverse sulcus............................................................. B. parvospinus

- Frons smooth, without broad transverse sulcus.............................................................. 2

2 Apices of fore and middle femora with black ring-like stripes.................................................. 3

- Apices of fore and middle femora without black stripes....................................................... 6

3 Frons with 1 longitudinal spot in middle................................................................... 4

- Frons without spot in middle; posterior margin of female subgenital plate nearly truncate.............. B. nigrigeniculatus

4 Posterior margin of female subgenital plate obtusely rounded.................................................. 5

- Posterior margin of femle subgenital plate nearly straight, emarginate................................... B. quadratus

5 Frons with 1 black spot in middle; pronotum and abdominal tergites with 1 black stripe in middle; lateral lobes of male subgenital plate with 1 apical process; female subgenital plate longer than wide, lateral margin triangular expanded in middle, posterior margin slightly projected in middle................................................................ B. trilobus

- Frons with 1 brown spot in middle; pronotum and abdominal tergites with 1 black brown stripe in middle; lateral lobes of male subgenital plate with obtusely rounded apex; female subgenital plate length equal to wide...................... B. fallax

6 Ovipositor with well-developed digitate lateral lobes at base of lower sheaths...................................... 7

- Ovipositor without digitate lateral lobes at base of lower sheaths........................................ B. digitatus

7 Posterior margin of female subgenital plate rounded................................................... B. bilobus

- Posterior margin of female subgenital plate truncate................................................ B. transversa