Key to species of Isopsestis Werny, 1968

1. Forewing ground color gray or gray-brown with clear crosslines................................................................................ 2

- Forewing ground color dark black, crosslines unclear ................................................................................................. 4

2. Uncus long, narrow at based, socii short and thin, fultura superior shield-shaped, valva with broad terminal process ........................................................................................................................................................................ I. cuprina

- Uncus long, broad at based, socii long and thick, fultura superior cup-shaped with with two prickly horns connected by spinulate area or bud-shaped, valva with narrow cucullus ...................................................................................... 3

3. Fultura superior cup-shaped with two prickly horns connected by spinulate area .................... I. poculiformis sp. nov.

- Fultura superior bud-shaped ................................................................................................................................ I. meyi

4. 8th segment broad and long, the caudal margin with shallowly incised, ductus bursae narrow................... I. naumanni

- 8th segment narrow and short, the caudal margin lobe-shaped, ductus bursae broad ....................................... I. moorei