Key to species of Thiallela based on adult

1. Postmedial line white................................................................................. 2

- Postmedial line black................................................................................. 4

2. Two discal spots fused, crescent-shaped................................................................... 3

- Two discal spots separated (Li & Ren 2006, Fig. 3).................................................. T. hiranoi

3. Forewings with a narrow white line edged along dorsal 2/5 of antemedial line (Li & Ren 2006, Fig. 2)......... T. platantra

- Forewings with a small white dot bordering antemedial line and adjacent to dorsal margin (Li & Ren 2006, Fig. 1) T. naevilla

4. Male flagellum with basal segments dilated, has a small notch near base......................................... 5

- Male flagellum simple, simple, basal segments not dilated, without notch........................................ 6

5. Male flagellum with first five segments dilated, sixth segment distinctly notched; forewing yellowish ocherous in basal major- ity region (Fig. 2).......................................................................... T. epicrociella

- Male flagellum with first three segments slightly dilated, fourth to sixth segments distinctly notched; forewing grayish yellow in basal majority region (Fig. 5)....................................................... T. sulciflagella sp. nov.

6. Forewing diffused lots of grayish white scales near antemedial line in basal region, antemedial line arched (Fig. 3) T. ligeralis

- Forewing without grayish white scales in basal region, antemedial line sinuate (Fig. 4)............. T. celadontis sp. nov.