The Th. signata species-group

Diagnosis. Members of the species-group are characterised by the limited sexual dimorphism expressed in the somewhat smaller and more rounded medial forewing spot in the females. In the male genitalia, the genital capsules of the majority of species are very similar and the diagnostic characters are found only in their phallus sizes and vesica structures. The vesica of the species-group is characterised by the short and conical distal diverticulum bearing a single cornutus, and the large ventral medial diverticulum (in proportion to the main chamber of the vesica). In the female genitalia, the posterior gelatinous enlargement of the corpus bursae is situated ventrally and has an appendix bursae originating from its posterior part.