Key to the species of the genus Tactusa in China based on male genitalia

1. Cucullus is not narrow and sickle-shaped.................................................................. 2

- Cucullus is narrow and sickle-shaped...................................................... T. virga (Figs 9, 17)

2. Right cucullus with a sickle-shaped process................................................................ 3

- Right cucullus without a sickle-shaped process............................................................. 4

3. Juxta with semi-circular opening dorsally for position of aedeagus............................. T. flexus (Figs 10, 18)

- Juxta with a deep cleft for aedeagus...................................................... T. pars (Figs 11, 19)

4. Aedeagus without a prominent dorsal plate................................................................ 5

- Aedeagus with a prominent dorsal plate.............................................. T. motuoensis (Figs 12, 20)

5. Juxta not triangle-shaped, without horn in centre............................................................ 6

- Juxta triangle-shaped, with horn in centre................................................... T. topi (Figs 13, 21)

6. Cucullus narrow and long, lengthwise extended..................................... T. discrepans (Figs 14, 15, 22)

- Cucullus broad, rounded, forming a cross with axis of valva.................................. T. brevis (Figs 16, 23)