Psychoides gosari sp. nov. is described in notes on biology in Korea. For the first time, it has been found that the larvae of this genus feed on fronds or sporangia of Dryopteris chinensis (Baker) Koidz., D. saxifraga H. Ito, D. bissetiana (Baker) C. Chr., D. crassirhizoma Nakai (Dryopteridaceae), and Athyrium yokoscense (Franch. et Sav.) Christ (Woodsiaceae), which are new host plants. Morphological descriptions, illustrations of adults, genitalia, and pupa, and the general biology are provided.