The external genitalia of the female holotype of Thitarodes armoricanus (Oberth��r, 1909) are illustrated and described for the first time. In addition, the genitalia of a male specimen attributed to this species are also described and illustrated. The lack of any or adequate illustrations of the female genitalia for most Thitarodes species precludes a comparative evaluation of the species represented by the holotype. The male genitalia of T. armoricanus show the presence of a strongly sclerotized basal spur on the valva that is characteristic of most Thitarodes species. On the basis of differences in forewing colour pattern we treat T. altissima (Daniel, 1940) stat. rest. as a distinct species. For clarification of Thitarodes��� taxonomy and systematics it is essential that detailed illustrations of male and female genitalia are published for all species to complement future morphological and molecular studies.