♂, Phuket, Thailand.		♂, Phuket, Thailand.
♂, Tak, Thailand.		♀, Tak, Thailand.
♂, Tak, Thailand.		♀, Tak, Thailand.
♂, Tak, Thailand.		♂, Mae Hong Son, Thailand.

ON : Papilio cocytus  Fabricius, 1787 OD : Mant. Ins. 2:29. TL : 'Siam' [Phuket (Pulau Salang)]. Distribution : S.Myanmar (Tenasserim to Mergui), W. to P.Thailand (Tak to Phuket). ● ssp.cocytus ● ssp.ambrysus ● ssp.aoyamai

Adolias satropaces Hewitson, 1876 : Ent. mon. Mag. 13:150-151. TL. Moulmein.

[ THAILAND ]
Tanaecia cocytus cocytus ; Pinratana & Eliot,1996 : 72, pl.47, figs.131,♂,♂(Un),♀. (Kanchanaburi; Prachuap Kirikhan) (in part)
Cynitia cocytus cocytus ; Okamoto et al.,2013 : 9. (Kanchanaburi: Mae Klong Station)
Cynitia cocytus cocytus ; Ek-Amnuay,2012 : 436, not fig. (Phuket) (in part)
Cynitia cocytus cocytus ; S.Sophonviwatkul, C.Sunthornwiphat & T.Laola,2015- : Butterflies of Thailand, fig. (Ratchaburi) (in part) (accessed: 2021.05.08)
Cynitia cocytus satropaces ; Kimura et al.,2016 : 101, figs.♂,♂(Un),♀,♀(Un). (Erawan WF; Hoi Yahn WF.)

[ THAILAND ]
Mae Hong Son : 1♂.

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Tak : 4♂ 2♀.

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Ratchaburi : 1♂ (photo by S.Sophonviwatkul).

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Phetchaburi : 7♂ 1♀ (photo by T.Aoyama and K.Yano).

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Phuket : 2♂.

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The butterfly is locally common in montane forest at low to moderate elevations (Alt. 100 - 900m) and males are territorial on shrubs or undergrowth.
Corbet,1941 assumed the type locality of cocytus as 'Pulau Salang' [Phuket]. I consider taxon satropaces is a synonym of it. Males of this population tend to increase in size from south to north, outer marginal band on the UpH is brownish, yellow ground color on the underside is paler, but is rather variable even within the same region.
A male example from Mae Hong Son seems closer to this subspecies. I provisionally treat it as ssp.cocytus, however further taxonomic study including more examples, especially females, is needed.

Fabricius, J.C.,1787 : Mantissa Insectorum sistens eorum species nuper detectas adiectis characteribus genericis,
differentiis specificis, emendationibus, observationibus.
Copenhagen, Christ. Gottl. Proft 8vo 1:xx+348pp ; 2:[2]+382pp

Hewitson, W.C.,1876 : Notes on Mr. Atkinson's collection of East Indian Lepidoptera,
with Descriptions of new species of Rhopalocera.
Ent. mon. Mag. 13:149-152.

Corbet, A.S.,1941 : Observations on Certain of the Fabrician Names onf Indo-Australian Rhopalocera (Lepid.)
Proc. R. ent. Soc. Lond. (B)10(6):98-106.

♂, Phetchaburi, Thailand. (photo by T.Aoyama)	♀, Phetchaburi, Thailand. (photo by T.Aoyama)
♂, Phetchaburi, Thailand. (photo by T.Aoyama)	♂, Phetchaburi, Thailand. (photo by T.Aoyama)
♂, Phetchaburi, Thailand. (photo by K.Yano)	♂, Ratchaburi, Thailand. (photo by S.Sophonviwatkul)

2007.01.31 - 2021.06.30.