The genus Cryptopsocus Li, 2002 is synonymized with Trichadenotecnum Enderlein, 1909. The type species of Crypto-psocus, T. cynostigmus (Li, 2002) n. comb., is considered to be a close relative of T. marginatum New & Thornton, 1976. These species cannot be assigned to any species group previously established in Trichadenotecnum so that the marginatum species group is here proposed for them. Three new species belonging to this species group are described: T. tigrinum and T. sharkeyi from Thailand and T. sabahense from Sabah, Malaysia. The phylogenetic position of the marginatum group is discussed using morphological data.
Species of the bark louse genus Trichadenotecnum Enderlein (Insecta: Psocodea) from Peninsular Malaysia and Singapore are revised with illustrations and identification keys. Twenty species are here recognised, with four new species and ten recorded for the first time from this region, together with an unnamed species represented by a single female. The previously described species T. marginatum New & Thornton is not included because its generic assignment is questionable. Females of T. cinnamonum Endang & New, T. imrum New & Thornton and T. sibolangitense Endang, Thornton & New, and the male of T. kerinciense Endang & New are described for the first time. A new species group is defined for T. krucilense Endang, Thornton & New.