Plutodes costatus Garaeus

Plutodes costatus (Butler, 1886: 53) (Garaeus)

(Figs 2–3, 29–30)

TL: Darjiling [Darjeeling] (West Bengal, India)

= Plutodes triangularis Warren, 1893: 388. (TL: Sikkim; Naga Hills (Nagaland, India))

Material examined: India, Arunachal Pradesh, Lower Subansiri dist.: 2 ♂, Old Ziro, 2.xi.2018, leg. M. Singh (13632–33/H10, NZCZSI); 2 ♂, 1 ♀, Old Ziro, 3.ix.2018, leg. R. Lenka & party (13634/H10, NZCZSI); West Kameng dist.: 1 ♀, Bomdila, 27.vi.2018, leg. M. Singh (13644/H10, NZCZSI); 2 ♂, 1 ♀, Lama Camp, Eaglenest WLS, 29.v.2019, leg. R. Lenka & party (13635/H10, NZCZSI); 1 ♀, Shergaon, 9.vii.2018, leg. M. Singh (13639/ H10, NZCZSI). Sikkim, South Sikkim dist.: 2 ♂, Ravangla, 23.vii.2019, leg. R. Lenka & party (13637/H10, NZCZSI); Gangtok dist.: 1 ♂, Singtam, 26.vii.2019, leg. M. Singh (13631/H10, NZCZSI); West Sikkim dist.: 1 ♂, Yuksom, 20.xi.2019, leg. A. K. Sanyal & party (13641/H10, NZCZSI). West Bengal, Darjeeling dist.: 1 ♂, Jhandi, 10.ix.2018, leg. R. Lenka & party (13630/H10, NZCZSI); 1 ♂, Echey Gaon, 15.ix.2018, leg. R. Lenka & party (13640/H10, NZCZSI); 2 ♀, Maneybhajang, 16.ix.2018, leg. M. Singh (13628/H10, NZCZSI); 1 ♂, Rimbick, 18.x.2018, leg. A. K. Sanyal & party (13642/H10, NZCZSI); 1 ♀, Palmajua, 3.xi.2018, leg. K. Bhattacharaya & party (13643/H10, NZCZSI); 1 ♂, Sitong, 31.vii.2019, leg. R. Lenka & party (13636/H10, NZCZSI); 1 ♂, Upper Kuwapani, 14.viii.2019, leg. R. Lenka & party (13629/H10, NZCZSI); Kalimpong dist.: 1 ♂, 2 ♀, Kolakham, 14.iv.2016, leg. A. K. Sanyal & party (13645/H10, NZCZSI), 1 ♂, 1 ♀ Rishop, 5.ix.2016, leg. K. Bhattacharaya & party (13638/H10, NZCZSI), 2 ♂, Lava, 9.xi.2016, leg. A. K. Sanyal & party (13646/H10, NZCZSI).

Diagnosis: Forewing length: ♂ 19–21 mm, ♀ 20–22 mm. The external morphology is similar to P. warreni Prout, 1923, but is distinct by the following characters: P. costatus is slightly larger having distinctly broader yellow costal margin with a larger triangular postmedial patch on forewing than P. warreni; the underside of forewing in P. costatus has a characteristic narrow, discal patch extending towards the inner margin and a dark, broad subapical patch reaching the middle of outer margin, whereas, in P. warreni the underside of forewing is of uniform pale brown colour without any discal line, but with a faint sub-apical blackish patch. The male genitalia in P. costatus are clearly distinctive, with a highly sinuous gnathos, well developed valva sacculus which has a broad, roundish ventral bulge on its slender acute distal extension. The valva sacculus in P. warreni is less sclerotized, slender, basally somewhat straight with a subapical thickening and a small, curved, acute apex distally. The aedeagus in P. costatus is broader, with vesica having a distal cornutus and a small patch of minute setae, while that in P. warreni is slender with vesica having a distal broad patch of minute spines. Plutodes costatus and P. warreni are also closely similar to the Indonesian P. thorbeni St ̧ning, 2010: 76 (figs 7–12) in the arrangement of yellow and brown patches on the wings. However, the apical patch on forewing in these two species is conspicuous, making them different from P. thorbeni, also underside and genitalia clearly distinguish them.

Distribution: India: Assam, Arunachal Pradesh, Himachal Pradesh (Shimla), Meghalaya (Khasis), Nagaland (Naga hills), Sikkim, West Bengal (Darjeeling, Kalimpong) (Warren 1893, Hampson 1895, Arandhara et al. 2017, Chettri & Yonle 2021, Sondhi et al. 2021). Global: China (Yunnan), Indonesia (Sumatra), Malaysia, Myanmar, Nepal, Thailand, Vietnam (Hồng & Sen 2018, Spitsyn et al. 2017, Sţning 2005, Yazaki 1993, 1994).

Remarks: P. costatus flies in the mid and upper montane moist deciduous and semi-evergreen undisturbed forests up to 2500 m altitude from May to the early half of November.