Species of Trouessartia known from the Hirundinidae appear to be associated with particular host genera, and it is common for two Trouessartia species to be associated with one host species. Of 17 Trouessartia species collected from Old World swallows and martins, 16 can be assigned to either the T. appendiculata or T. minutipes complexes. The 8 Old World species in the appendiculata complex will be briefly (re)described and figured: T. appendicu!ata (Berlese) from Hirundo species; T. eximia, n. sp. and T. santanai, n. sp. from Riparia paludicola; T. g!adijera, n. sp. from Delichon species; T. longiseta, n. sp. from Cecropis species; T. modesta Gaud and Mouchet from Psalidoprocne species; T. piscicauda Gaud from Riparia riparia; and T. sophiae, n. sp. from Phedina species. T. crucijera Gaud is included in the key to species, but this taxon can not be assigned to either of the species complexes..