Key to the species of the genus Monastria

1 Female pronotum with acute lateral angles; absence of notch or spines (Fig. 9A, B) ............................... M. angulata Saussure

- Male and Female pronotum with sharp or rounded lateral angles; with notch or spines..............................................................2

2 Female tegmina long, reaching the fifth abdominal tergite; hind margins curved and rounded. Male with L1 sclerite with lateral branch curved, rounded and with some small spines ....................................................................................................................3

- Female tegmina short, not extending further than the fourth abdominal tergite; hind margin truncated or with a curvature. Male with L1 sclerite with lateral branch slightly curved forward, with the aspect of a big sharp tooth ..............................................4

3 L1 sclerite with lateral branch curved, rounded and smooth with some small spines; R3d sclerite with a clear prominence like a tooth in ventral view (Fig. 14) ................................................................................................................... M. kaingangue sp. n.

- L1 sclerite with lateral branch curved and rounded with large spines directed downwards (Fig. 8); R2 sclerite shorter and forming a right angle.............................................................................................................................................. M. similis (Serville)

4 Male L1 sclerite with a big lateral dilatation and an edge in the posterior median region (Fig. 10). Female supra-anal plate with straight posterolateral angles .............................................................................................................................. M. cabocla sp. n.

- Male L1 sclerite without a big lateral dilatation and an edge in the median region. Female, supra-anal plate posterolateral angles rounded..........................................................................................................................................................................................5

5 L1 sclerite slightly concave region with irregular distal margins with grooves (Fig. 11). Female frons with a prominence ......... ............................................................................................................................................................................. M. itubera sp. n.

- L1 sclerite without slightly concave region and irregular distal margins with grooves. Female frons flat ..................................6

6 L1 sclerite with lateral branch slightly curved with some spines reaching the crown of spines at the posterior region (Fig. 13). ............................................................................................................................................................................ M. itabuna sp. n.

- L1 sclerite without lateral branch with some spines reaching the crown of spines in the posterior region ..................................7

7 L1 sclerite with a sharp dorsal protuberance and with a projection in the right side turned forward; L2d sclerite, hook with internal ventral margin concave (Fig. 5) ................................................................................................ M. biguttata (Thunberg)

- L1 sclerite with a roughly triangular spear-shaped apical region, hind margin with a large non-sclerotized projection. L2d sclerite, hook with internal ventral margin strongly convex (Fig. 16)........................................................................ M. sagittata sp.n