Gamasamorpha cataphracta KARSCH, 1881 is redescribed on the types; synonym of it is Oonops corticalis BÖSENBERG & STRAND, 1906 (types examined; new synonymy). Pseudotriaeris n. gen. is described; type: Gamasomorpha karschi BÖSENBERG & STRAND, 1906), of uncertain affinities this genus is peculiar by the extreme complexity of the _??_-palp. Pseudotriaeris karschi (BÖSENBERG & STRAND, 1906) comb. nov. is redescribed on the types. From Formosa are recorded or described: Gamasomorpha cataphracta KARSCH; Ischnothyreus formosus n. sp. (_??__??_; type. loc.: Akau), near to I. narutomii (NAKATSUDI, 1942), distinguishable from this and the other species by the genitalia; Opopaea sauteri n. sp. (_??_, _??_ unknown; typ. loc.: Takao), near to O. syarakui (KOMATSU, 1967) comb. nov. (described as Gamasomorpha), distinguishable by the genitalia. Some considerations are made over taxonomical problems in the genera Gamasomorpha and Opopaea.