Key to the species of the subgenus Acanthosia (based on male genitalia)

1 Male genitalia with thick acute process (cp in Fig. 6A) in middle of dorsal margin of ala valvae............. flavifrontella

- Ala valvae without process on dorsal margin, with acute dorso-basal process (dp in Fig. 6C).......................... 2

2 Processus basalis plicae roundish, flat (Fig. 15B in Birket-Smith 1965).................................... duplicata

- Processus basalis plicae digitiform (pb in Fig. 6C)........................................................... 3

3 Dorso-basal nearly straight pointed process on the valva (pp in Fig. 13B in Birket-Smith 1965)................... similis

- Dorso-basal pointed process, bent mesad near its base, on the valva (dp in Fig. 6C)........................... tryphosa

Key to the species of the subgenus Acanthosia (based on female genitalia)

1 Ductus bursae long and slender; lamella postvaginalis concave, without median swellings............................ 2

- Ductus bursae fairly broad, forming cervix; lamella postvaginalis concave, with median swelling...................... 4

2 Ductus bursae as long as diameter of corpus bursae or longer................................................... 3

- Ductus bursae shorter than diameter of corpus bursae (Fig. 8A)...................................... brevis sp. nov.

3 Corpus bursae basically oval; ductus with sclerification posteriorly (Fig. 7E).......................... oblonga sp. nov.

- Corpus bursae spherical; ductus with annular scobination anteriorly (Fig. 7A)........................... flavifrontella

4 Ductus bursae squat, roughly cylindrical; corpus bursae pouch-like (Fig. 9A)............................ parva sp. nov.

- Ductus bursae elongated; corpus bursae spherical............................................................ 5

5 Ductus bursae slightly longer than corpus, funnel-shaped: posteriorly broad, narrowing at the corpus bursae junction (Fig. 14 in Birket-Smith 1965).............................................................................. similis

- Ductus bursae shorter than corpus, cylindrical (Fig. 17 in Birket-Smith 1965)............................... duplicata