ON : Dercas difformis Nicéville, 1898 OD : Ann. Mag. nat. Hist. (7)2: 483. TL : 'Western and Central China'. Distribution : Sichuan, Vietnam, Guangxi to Zhejiang, Hubei.

Dercas enara Swinhoe, 1899 : Ann. Mag. nat. Hist. (7)3: 107. TL. "Omei-shan, W.China" [Emei Shan, Sichuan].

[ LAOS ]
Dercas lycorias f. difformis ; Dubois & Vitalis,1921 : 21. (Laos)
Dercas lycorias f. lycorias ; Dubois & Vitalis,1921 : 21. (Laos)
Dercas lycorias lycorias ; Masui & Uehara,1997 : 6, pl.2, figs.12,♂,♂(Un). (Lak Sao)
Dercas lycorias lycorias ; Osada, Uémura & Uehara,1999 : 203, pl.39, figs.♂,♂. (Xam Neua; Lak Sao)
Dercas lycorias ; Nakamura & Wakahara,2012 : 43.
Dercas lycorias lycorias ; Onodera,2022 : 18, pl.69, figs.♂,♂(Un), text:18. (Bolikhamxai: Lak Sao)
Dercas lycorias lycorias ; Inayoshi,1996-2023 : Butterflies in Indo-China. (by literature) (31.Dec.2023 last updated ; 30.Apr.2025 changed.)

[ VIETNAM ]
Dercas lycorias f. difformis ; Dubois & Vitalis,1921 : 21. (Annam)
Dercas lycorias f. lycorias ; Dubois & Vitalis,1921 : 21. (Tonkin: Chapa)
Dercas lycorias f. decipiens ; Dubois & Vitalis,1921 : 21. (Annam: Muong-Sen)
Dercas difformis ; Lemée,1950 : 5. (Hagiang)
Dercas lycorias difformis ; Metaye,1957 : 86. (C)
Dercas lycorias lycorias ; Metaye,1957 : 86. (N)
Dercas lycorias lycorias f. decipiens ; Metaye,1957 : 86. (C)
Dercas lycorias lycorias ; Monastyrskii & Devyatkin,2015 : 17. (N / C)
Dercas lycorias lycorias ; Inayoshi,1996-2023 : Butterflies in Indo-China. (by literature) (31.Dec.2023 last updated ; 30.Apr.2025 changed.)
Dercas lycorias difformis ; Monastyrskii,2024 : 108-109, pl.27, figs.3a♂,3b♂,3c♂(Un),3d♀,3e♀(Un). (N: Hoang Lien; Cong Troi; Cat Cat; Ha Giang / C: Vu Quang; Phong Nha-Ke Bang; Bach Ma; Ngoc Linh; Kon Plong; Chu Yang Sin)

[ THAILAND ]
' Siam. 2♂ (NHML, ex.Grose-Smith,1910)'

[ VIETNAM ]
Lao Cai : 2♂ (NHML).
'Cochin China', Laokai [Lao Cai]. 1936.06.--. 1♂ ; 'Cochin China;, Chapa' [Sapa]. 1936.08.--. 1♂.

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Bozano et al. (2016: 37) assumed that the taxon difformis is a synonym of the nominotypical subspecies. Although it has many taxonomic problems, difformis is tentatively treated here as a separate subspecies. Further taxonomic study is needed.
There are several specimens labelled 'Siam' in the NHML, but no detailed data is available and it is considered to be an erroneous locality.

Nicéville, L. de,1898 : A Revision of the Pierine Butterflies of the Genus Dercas.
Ann. Mag. nat. Hist. (7)2: 478-484.

Swinhoe, C.,1899 : New Species of Orientali Lepidoptera.
Ann. Mag. nat. Hist. (7)3: 102-116.

Wu, C.,2010 : Fauna Sinica, Insecta vol.52, Lepidoptera Pieridae.
Science Press, Beijing, China. 416 pp., 16 col pls. (in Chinese)

Bozano, G.C., Coutsis, J., Herman, P., Allegrucci, G., Gesaroni, D. & Sbordoni, V.,2016 :
Guide to the Butterflies of the Palearctic Region. Pieridae part 3. Subfamily Coliadinae, Dismorphinae
70 pp., Omnes Artes, Milano.

Yoshino, K.,2023 : Review of the taxonomic classifications of Chinese butterflies (1) (Papilionidae, Pieridae, Nymphalidae and Hesperiidae, Lepidoptera)
Neo Lepidoptera 5: 32-45.

2025.04.30.