♂ (dsf), Chanthaburi, Thailand.		♂ (wsf), Phetchabun, Thailand.
♂ (dsf), Chiang Mai, Thailand.		♂ (dsf), Nan, Thailand.
♂ Nakhon Si Thammarat, Thailand. (photo by A.Giudici)		♂ (dsf) Lampang, Thailand.

ON : Celastrina howarthi Cantlie & Norman, 1960 OD : J. Bombay nat. Hist. Soc. 57(2):427-428. TL : "Sibsagar dist." [Sibsagar Dist., Assam]. (NHML) Distribution : Assam to Myanmar, Thailand, Laos, Cambodia, Vietnam.

Holotype ♂, Sibsagar Dist., Assam, India. (NHML)

[ THAILAND ]
Udara placidula ssp. ; Pinratana,1981 : 47. 163. not fig. (Chiang Mai)
Udara placidula howarthi ; Ek-Amnuay,[2007] : 564, pl.256, figs.L91,♂,♂,♂(Un). (Chiang Mai)
Udara placidula howarthi ; Ek-Amnuay,2012 : 584, pl.264, figs.L116,♂,♂,♂(Un). (Chiang Mai)
Udara placidula howarthi ; Kimura et al.,2014 : 192, figs.♂,♂(Un),♂,♂(Un). (Doi Pha Hom Pok; Doi Suthep; Nakohn Nayok; Kao Soi Dao; Kao Saverb)

[ LAOS ]
Udara placidula howarthi ; Motono & Negishi,1989 : 70, pl.100, figs.A7,♂,A8,♂(Un). (Luang Prabang; Nam Moh; Phatong)
Udara placidula howarthi ; Osada, Uémura & Uehara,1999 : 214, pl.109, figs.♂,♂,♂(Un). (Lak Sao; Thabok)
Udara placidula howarthi ; Onodera,2009b : 37,41. (Xieng Kouang: Nam Noen; Khammouan: Nacay)
Udara placidula howarthi ; Nakamura & Wakahara,2012 : 51, pl.14, fig.Ly-37,♀,♀(Un). (Xieng Khouang)
Udara placidula howarthi ; Onodera,2022 : 75, pl.206, figs.♂,♂(Un),♀,♀(Un). (Khammouan: Nakai; Xiang Khouang: Phon Kham)

[ CAMBODIA ]
Udara placidula howarthi ; Monastyrskii et al.,2011 : 130. (Phnom Samkos W.S.)
Udara placidula howarthi ; Chartier & Kosterin,2022 : 120. (Pursat)

[ VIETNAM ]
Udara placidula howarthi ; Ikeda et al.,2001 : 48, figs.2:9,♂,10,♂(Un),6:12(♂genitalia). (Cuc Phuong)
Udara placidula howarthi ; Luong et al.,2004 : 9. (Cuc Phuong)
Udara placidura [sic] howarthi ; Miyazaki, Saito & Saito,2006d : 53, figs.L-28,♂,♀. (Lam Dong: Dambri; Dai Duc Me; Gung Re)
Udara placidula howarthi ; Monastyrskii & Devyatkin,2015 : 51. (N / C)

[ THAILAND ]
Mae Hong Son : 3♂.

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Chiang Mai : 5♂ (1♂ genitalia dissected).

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Lampang : 1♂.

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Nan : 3♂.

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Tak : 1♂.

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Phetchabun : 1♂.

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Chanthaburi : 1♂.

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Nakhon Si Thammarat : 4♂ (incl. photo & photo by A.Giudici), (1♂ genitalia dissected).

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[ LAOS ]
Sekong : 1♂.

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The butterfly is locally not rare in montane forests at low to moderate elevations (Alt. 100 - 1200m). Males frequently come to the banks of streams and puddles to suck water.
The population from Nakhon Si Thammarat is considered to be this taxon.

Cantlie, K. & Norman, T.,1960 : Four new butterflies from Assam.
J. Bombay nat. Hist. Soc. 57(2):424-429. (5 fgs)

♂ with Discolampa ethion, Phetchabun, Thailand.	♂ (dsf), Lampang, Thailand.
♂, Nakhon Si Thammarat, Thailand. (photo by A.Giudici)	♂, Nakhon Si Thammarat, Thailand.

1999.06.25 - 2023.03.31.