Marumba cristata (Butler, 1875)

Transferred to Marumba by Kirby, 1892, Synonymic Cat. Lepid. Heterocera 1: 707. Erroneously synonymized with Polyptychus dyras by Hampson, 1893, Fauna Brit. India 1: 69. Reinstated as a species by Rothschild & Jordan, 1903, Novit. zool. 9 (suppl.): 269 (key), 272. Marumba cristata, like other species of Marumba and indeed many Smerinthini, exhibits a considerable amount of intraspecific variation in both wing pattern and genital structure. Indeed, it can often be difficult to find two specimens that are identical, as Kitching & Cadiou (2000: 147) discovered for Marumba sperchius. They concluded that “the individual variation in the male genitalia in sperchius is so great that its use in diagnosing subspecies is largely precluded” and that “such individual variation in the structure of the male genitalia is typical of all species of Marumba”. Nevertheless, despite discovering that this situation also applied to Marumba cristata, Eitschberger (2015) nevertheless raised all the taxa hitherto treated as subspecies to full species status and then described an additional two species, all of which he justified on the basis of perceived differences in the male genitalia and, in the case of the island populations, “the inertia of the females”, stating that the lack of observations of female Marumba cristata at lights on ships implied that females did not cross stretches of water between islands. Of course, absence of evidence does not constitute evidence of absence and this argument is thus rejected here, together with his oversplit taxonomy. However, despite the lack of consistent and discrete morphological differences between any populations of Marumba cristata, DNA barcode evidence (which Eitschberger (2015) summarily dismisses as irrelevant) does suggest that there are subtaxa within Marumba cristata that warrant recognition and, given the morphological coherence of the group as a whole, these are treated here as subspecies. Whether the separation of Marumba cristata titan from the nominotypical subspecies, Marumba cristata cristata, is justified remains to be determined. Eitschberger (2015) treated all Mainland Asian populations, with the exception of those he assigned to “Marumba centrosinica” (see Marumba cristata centrosinica), as belonging to “Marumba cristata”, and restricted “Marumba titan” to the Sumatran population on the basis of its “relatively good isolation”. However, as pointed out by Brechlin (2014), analysis of DNA barcode data shows no significant differences between the Sumatran population and samples from NE India (Assam), SW, SE and E China (Yunnan, Hainan, Jiangxi), Burma, Thailand, Vietnam and Peninsular Malaysia. Eitschberger (2015) just dismissed this evidence, and simply asserted that “Due to the isolation as well as the genital morphology, even if the differences are hard to explain or prove, this issue does not arise for me, even if the genetic difference between the mainland and the island species is very low – for me, the difference could also be zero”, and treated titan as a species. However, evidence must be assessed, not just dismissed. So, until further data is forthcoming to demonstrate otherwise, on the basis of the DNA barcode sequences, all the above populations are treated here as Marumba cristata titan (q.v.). However, given that the type locality of Marumba cristata is the “vicinity of Darjeeling”, the possibility also remains that the populations from north and west of the Brahmaputra River (Arunachal Pradesh, west through Bhutan, Sikkim and Nepal, to Uttaranchal) may represent a subspecies distinct from Marumba cristata titan and be assignable to a separate nominotypical subspecies. However, as yet, there are no DNA data to determine whether this is the case or whether Marumba cristata titan should simply be synonymized with the nominotypical subspecies (morphology, of course, being of no use in reaching a conclusion). For the moment, so as to put out the hypothesis for testing, the above separation between Marumba cristata cristata and Marumba cristata titan is provisionally adopted.