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Genus Tactusa Fibiger , new genus
Type-species: Tactusa sumatrensis Fibiger , new species.
Taxonomic notes. The genus Tactusa includes 27 known species, placed in 4 species-groups: T. major species-group; T. trigonifera species-group; T. nieukerkeni species-group and T. artus species-group. Except that they share several prominent structural features, they are regarded as modifications within the generic ground plan of the genus. With only a few exceptions, the species can be recognised only by structures in the male and female genitalia.
Imago (external). Thorax, tegulae and ground-colour of forewing: light yellowish brown, forewing often with a well-marked quadranglar or triangular costal patch between antemedial and postmedial lines.
Reniform stigma: outlined by large costal patch; often difficult to observe.
Hindwing: dark greyish; with brown terminal line and indistinct discal spot; without medial line.
Male genitalia. Tegumen: narrow, considerable narrower than vinculum and saccus (apo).
Vinculum: strongly built.
Saccus: short; strongly built, broadly U shaped.
Fultura superior: membranous.
Ampulla: more or less forming a cross with axis of valva; elongated and narrow (apo.) (shorter by T. ostium ); convex by valva; distal edge concave; some species distally with short, stout spines, and with differently shaped inner and outer edges.
Digitus: usually absent; present in one species group.
Juxta and anellus plate: totally fused, with hole for phallus; slightly asymmetrical.
Phallus: long; coiled clockwise, tapered towards apex; coecum upturned only in type-species); with humps subbasally; almost straight until strong coil subterminally in a few species; subapically with a prominent, long spine, also in a few species; some species with a shorter straight cylinder; and some with less prom-
Female genitalia. Ovipositor: quadrangular with rounded corners.
Anterior apophyses: longer than posterior apophyses (apo.).
Ostium: displaced to left.
Antrum: cylindrical; short; narrow; heavily sclerotised (apo.).
Ductus bursae: membranous, long, narrow; slightly coiled.
Appendix bursae: arising anteriorly from ductus bursae, immediately posterior to antrum.
Corpus bursae: globular.
Signum: cross shaped.
Distribution. Genus occurs in tropical and subtropical areas of SE Asia and Oriental regions.
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