HOLOTYPE ♂ Vietnam: Bach-Ma National Park, 16°10'N 107°54'E, 1200m, 26.vii-6.viii.1996 (Sinjaev & Afonin) (ex coll. R. Brechlin) [CTWM].
Synonymized with Callambulyx kitchingi by Eitschberger & Nguyen, 2018, Neue Ent. Nachr. 75: 2. Reinstated as a species by Brechlin, 2019, Entomo-Satsphingia 12 (2): 79.
Callambulyx kitchingi was described by Cadiou (1996) (STI 17134) based on a holotype and five paratypes from SE China (Fujian and Jiangxi), and an additional specimen from Sichuan. Shortly afterwards, Brechlin (1997) (STI 16985) described Callambulyx schintlmeisteri from a holotype and one paratype from Bach-Ma National Park in central Vietnam. Unfortunately, despite the close similarity in habitus of the two taxa, the description of Callambulyx schintlmeisteri did not include a comparison with Callambulyx kitchingi, possibly due to the short time interval between the two publications, possibly due to Brechlin being unaware of Cadiou’s paper (which was published in the journal Entomologia Africana, an odd choice for an Asian taxon). Eitschberger & Nguyen (2018) (STI 21890) studied the habitus and male genitalia of specimens of Callambulyx kitchingi from northern Vietnam (Lang Son) and various localities in southern China (Fujian, Jiangxi, Hainan, Hunan) finding no differences in habitus, and differences in genital morphology were considered to be intraspecific variation. On these grounds, they synonymized Callambulyx schintlmeisteri from central Vietnam (Bach Ma N.P. and the Ba Na Hills) with Callambulyx kitchingi. However, it is difficult to understand why, when they had a male from central Vietnam (Da Nang, Ba Na Hills, Nui Chua), Eitschberger & Nguyen (2018) (STI 21890) did not dissect this specimen to examine its genitalia. It is true that the drawings and photographs in Cadiou (1996) (STI 17134) and Brechlin (1997) (STI 16985) leave much to be desired in terms of clarity and consistency of viewing angle, and, as Eitschberger & Nguyen (2018) (STI 2180) illustrated, the male genital morphology of Callambulyx kitchingi, like many Smerinthinae, is highly individually variable, but a direct comparison between specimens from central Vietnam and those from northern Vietnam and China would have been instructive, even if the differences (if any) might be expected to be small.
Study of DNA barcode sequences suggests the synonymy is incorrect. Fourteen samples of Callambulyx kitchingi in BOLD (as of 18.xii.2018), 13 from China and one from Lang Son, Vietnam, show pairwise divergences ranging from 0% to 0.93%, well within the range of individual variation of a smerinthine species. Furthermore, the divergences between the Vietnamese sample and those from China range from 0.16% to 0.64%, also well within the overall range for a smerinthine species. Thus, there is no question that Eitschberger & Nguyen (2018) (STI 21890) were correct in determining the conspecificity of these populations. However, the three samples in BOLD from central Vietnam identified as Callambulyx schintlmeisteri, which have inter-sample divergences of 0% to 0.25%, show much greater differences from the more northern samples, ranging from 3.4% to 6.02%. In particular, the divergences between the central and northern Vietnamese samples range from 3.96% to 5.74%. Such differences would generally suggest the two clusters are separate species not conspecific.
A comparison of the habitus of the small series of Callambulyx kitchingi (n = 15) and Callambulyx schintlmeisteri (n = 1) in the NHMUK, together with those illustrated by Eitschberger & Nguyen (2018) (STI 21890), did not reveal any consistent differences, other than the NHMUK Callambulyx schintlmeisteri being perhaps slightly larger and with slightly more falcate forewing apices. Consequently, the conclusions of Eitschberger & Nguyen (2018) (STI 21890) could not be refuted and so, despite the large DNA barcode divergences, the synonymy of Callambulyx schintlmeisteri with Callambulyx kitchingi was, at that time, provisionally accepted, pending further detailed study of the morphology, particularly the genitalia.
Subsequently, Brechlin (2019) (STI 22002) provided this further study of the morphology of Callambulyx schintlmeisteri, noting a diagnostic feature relative to Callambulyx kitchingi in the shape of the antemedial line on the forewing upperside (see Media) and differences in the male genitalia (see Diagnostic Description). Consequently, the reinstatement of Callambulyx schintlmeisteri as a species was accepted.