So far, seven species of
Rhyacionia Hübner have been recorded in Japan. Among them, five species,
R. dativa Heinrich,
R. washiyai (Kôno and Sawamoto), sp. rev.,
R. pinivorana (Lienig and Zeller),
R. simulata Heinrich, stat. rev. and
R. vernalis Nasu and Kawahara, were really found in Japan, but the occurrence records of the remaining two,
R. pinicolana (Doubleday) and
R. buoliana ([Denis and Schiffermüller]), were expunged, because they were elucidated to be based on the misidentification of
R. washiyai and
R. dativa, respectively.
R. washiyai types were discovered, and the lectotype was designated here and preserved in the National Science Museum, Tokyo, Japan. The species was treated as a junior synonym of
R. dativa; however, they are quite different species.
R. washiyai is externally similar to
R. pinicolana distributed in Europe and Russia, but it is distinguishable from the latter in having a cucullus without a ventral process in the male genitalia.
R. simulata was treated as a subspecies of
R. duplana (Hübner); however, it is regarded as an independent species in having peltate signa instead of horn-shaped ones in
R. duplana in the female genitalia. Matsumura treated
Evetria buoliana in his book published in 1917, but he used another name,
E. japoniella Matsumura, in the figure legend of the species. The name
japoniella was treated as a junior synonym of
R. dativa; however, the name was unavailable as per articles 11.6 and 11.6.1 of the International Code of Zoological Nomenclature (4th edition) because it was originally published as a junior synonym of
buoliana and was not adopted as the name of a taxon before 1961. The adults and
genitalia of the Japanese species were illustrated, and the distinguishing characteristics among the species and keys to species based on external and genitalic characteristics were given.
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