| abstract | Two new species of the feather mite genus Trouessartia (Analgoidea: Trouessartiidae) are described from tyrant flycatchers (Tyrannidae) in Argentina: Trouessartia salvadori sp. nov. from the White-crested Tyrannulet Serpophaga subcristata (Vieillot) and T. gonzalezacunai sp. nov. from the Vermilion Flycatcher Pyrocephalus rubinus (Boddaert). Trouessartia salvadori sp. nov. is close to T. longiducta and most clearly differs from the latter in having, in males, the genital apparatus with wedge-shaped hyaline extensions and the anterior genital papillae situated more distant from the midline than posterior ones, and in females, setae h1 not extending beyond the margin of the interlobar membrane, and the posterior part of the hysteronotal shield bearing well outlined ovate lacunae except in the narrow median area. Trouessartia gonzalezacunai sp. nov. is similar to T. savanae , but is distinguished from that species in having, in males, the terminal lamellae shaped as a fishtail, the epiandrum shaped as a goblet, the apophyses of adanal apodemes represented by thick spine-like tubercles, and in females, setae h1 minute spiculiform about 10 long, and the external copulatory tube shaped as a small rounded tubercle near the margin of interlobar membrane. |