Key to species of the genus Lacusa Stål, 1862 (modified from Xing & Chen 2014)

1. Tip of the tegmina bearing a branched pattern (Fig. 63) ................................................................... 2

– Tip of the tegmina bearing an unbranched pattern (Fig. 74) ................. L. fuscofasciata (Stål, 1854)

2. Median periandrium processes long, extending beyond the apex of periandrium dorsally ................ .......................................................................................................... L. producta Xing & Chen, 2014

– Median periandrium processes short, not extending dorsally beyond the apex of periandrium (Fig. 70, Mpp) ................................................................................................................................. 3

3. Median extension of periandrium as developed as paired median processes of the periandrium....... ............................................................................................................ L. digitata Xing & Chen, 2014

– Median extension of periandrium longer and wider than paired median processes of the periandrium (Fig. 70) .................................................................... L. yunnanensis Chou & Huang, 1985 stat. rev.