Key to species of Thiallela based on female genitalia

1. Eighth sternite with a pair of processes on posterior margin................................................... 2

- Eighth sternite without process on posterior margin......................................................... 4

2. Ductus bursae shorter than antrum (Li & Ren 2006, Fig. 10).......................................... T. platantra

- Ductus bursae longer than antrum....................................................................... 3

3. Signum L-shaped (Yamanaka 2002, Fig. 10)........................................................ T. hiranoi

- Signum bending horn-like (Li & Ren 2006, Fig. 9)................................................... T. naevilla

4. Antrum with width not longer than twice of length.......................................................... 5

- Antrum with width longer than twice of length............................................................. 6

5. Signum a small, bending horn (Fig. 14)............................................................ T. ligeralis

- Signum a large, boomerang-shaped horn (Fig. 16)......................................... T. sulciflagella sp. nov.

6. No sclerite posterior to eighth abdominal segment; signum a strong bending horn (Fig. 13)................ T. epicrociella

- A sclerite posterior to eighth abdominal segment; signum straight, clubbed (Fig. 15)................ T. celadontis sp. nov.