The epicopeiid moth genus Schistomitra Butler, 1881 is reported outside Japan for the first time, with a new species, Schistomitra joelmineti Huang & Wang, sp. nov., described from the southern part of Shaanxi and Gansu Province in China. Photographs of adults and genitalia are provided, and the distribution pattern of the genus is discussed.

East Asia, Geometroidea, host plant, oriental swallowtail moth, Stewartia, taxonomy

Epicopeiidae Swinhoe, 1892, commonly known as oriental swallowtail moths, belongs to the superfamily Geometroidea within Macroheterocera sensu Mitter et al. (2017). Hitherto this small family is comprised of 10 genera and less than 30 species restricted in the Asian Palaearctic and Oriental regions. The family can be distinguished by having a head without ocelli, forewing without an areole and in the forewing venation – vein R₅ usually stalked with vein M₁ (Minet 2003). Members of the family nearly all come out at day with few exceptions, and are usually mimickers of some diurnal lepidopterous families such as Papilionidae, Pieridae, Riodinidae and Zygaenidae. Immature stages are only known in the genera Epicopeia Westwood, 1841, Psychostrophia Butler, 1877 and Schistomitra Butler, 1881, and their larva and pupa are covered by a waxy substance on the surface (Janet and Wytsman 1903, Sugi 1972, Nakamura 2006).

The genus Schistomitra was erected by Butler in 1881 based on its type species, S. funeralis Butler, 1881. It is characterized by the following two characters: labial palpi entirely blackish brown and gnathos represented by a pair of short and sclerotized arms which are dentate dorsally (Minet 2003). Externally Schistomitra is unique within Epicopeiidae by imagoes having an extensive pale yellowish ground color which is divided into patches of different sizes and shapes by blackish patterns on the upper sides of wings. Adults of S. funeralis are diurnal, occurring from late spring to early summer, with numbers usually peaking between mid-May and mid-June. They can be found sucking nectar from flowers and water on damp ground. The larva, covered externally by waxy matter commonly found in other Epicopeiidae larvae, feeds on Stewartia pseudocamellia (Korean stewartia, Japanese stewartia, or deciduous camellia). It overwinters as a pupa (Sugi 1972).

Inoue (1982) established Schistomitrinae based on the genus Schistomitra, which contained two genera from Japan, viz. Schistomitra Butler, 1881 and Psychostrophia Butler, 1877, as a new subfamily under Epiplemidae (now the Epipleminae under Uraniidae). Minet (2003) synonymized Schistomitrinae with Epicopeiidae because in the analysis based on morphological characters proposed in the same paper, Schistomitra was found to be the sister group of the clade (Nossa Kirby, 1892 + Epicopeia Westwood, 1841); thus, there was no need to maintain this subfamily. In the molecular phylogenetic tree proposed in Wei and Yen (2017), Schistomitra was found to be the sister group of either the clade (Chatamla Moore, 1881 + Mimaporia Wei & Yen, 2017) or the clade (Chatamla Moore, 1881 + Mimaporia Wei & Yen, 2017 + Parabraxas Leech, 1897). Hence, the precise relationships between these genera is still unclear and needs further investigation.

For a long time, Schistomitra was regarded as an endemic Japanese genus only found in Honshu, Shikoku, and Kyushu (Sugi 1972, Owada 2011, Association of Aso area world agriculture inheritance promotion 2014). Unexpectedly, recently we received some interesting epicopeiid moth material which was collected from southern Shaanxi and Gansu from 2007 to 2017, and they shared many external similarities with the genus Schistomitra. After examining the genitalia and comparing them with those of Schistomitra funeralis, all the results lead to a conclusion that these materials belong to an undescribed species of the genus Schistomitra and it is described here.

Specimens examined in this study were all collected during the day with an insect net and are deposited in the collection of South China Agricultural University (SCAU), Guangzhou, PR China and the Bavarian State Collection of Zoology (Zoologische Staatssammlung München), Munich, Germany (ZSM). All adult photographs in the laboratory were taken with a Nikon CoolPix S7000 camera, the adults in wild and habitat photos were taken with a Canon EOS 80D camera by collector Mr Wen-hao Sun. Abdomens were removed and macerated in 10% NaOH for examination of male and female genitalia. Photographs of genitalia were all taken under a Keyence VHX-5000 digital microscope, and were all processed by Adobe Photoshop CS5 software. Terminology of adult morphology and genitalia follows Klots (1970), Kristensen (2003), Minet (2003), and Wei and Yen (2017).

Although the external features of adults of Schistomitra joelmineti are variable among individuals to some extent, their genitalia are only slightly different in the tip of the uncus, length of the aedeagus, and width of the pointed process in the praesacculus, while they differ greatly from those of S. funeralis. Thus, we regard all these individuals from China as a single species.

The genus Schistomitra currently shows a disjunct distribution with the discovery of Schistomitra joelmineti, with one species found in the mountainous region around Mt. Qinling in Shaanxi Provinceand Gansu Province in China and the other in Honshu, Shikoku, and Kyushu in Japan (Fig. 24). The disjunct distribution might be caused by the distribution pattern of their host plants. The host plant genus Stewartia is widely distributed in Honshu, Shikoku, and Kyushu in Japan, the southern part of the Korean Peninsula, as well as in the vast area between Mt. Qinling and Mt. Nanling in China (Li 2011), which could explain the absence of this moth genus in northeastern, northern China and the northern part of the Korean Peninsula. However, it is still a mystery as to why this genus is not found in the southern part of the Korean Peninsula, but this will only be solved with careful and intensive collecting in the suitable habitats, to determine its biogeography. In addition, S. funeralis tends to be distributed in mountainous areas with a rather dry climate in Japan, where annual precipitation is no more than 1800 mm (Sugi 1972). Similarly, the mountainous regions in southern Shaanxi and Gansu are also rather cool and dry with an annual precipitation of no more than 1300 mm, similar to the habitats of S. funeralis in Japan. Thus, the narrow distribution of Schistomitra in southern Shaanxi and Gansu may relate to its intolerance of high temperatures or humid climates; in other words, the hot and humid climate of other regions may have played an important role in preventing the extension of this genus to southern and southeastern China.

Figure 24. 

Distribution map of the genus Schistomitra. Records of distribution are taken from Sugi (1972), Association of Aso area world agriculture inheritance promotion (2014), and the present study.

Speciation in Schistomitra may mostly be the result of isolation mechanisms mentioned above. In addition, the utilization and distribution of different host plants may also contribute to it to some extent. In the phylogenetic tree of Stewartia proposed by Li (2011) based on morphological characters, Stewartia pseudocamellia, the host plant of Schistomitra funeralis, was not recovered in the same clade as the only species of Stewartia found in southern Shaanxi, Stewartia shensiensis (which might be the candidate host plant of Schistomitra joelmineti). In Lepidoptera, a similar case exists in the lycaenid butterfly genus Sibataniozephyrus Inomata, 1986, which is widespread in Japan, Taiwan, and the southern, southwestern and central part of mainland China, and diverges into three species utilizing different species of Fagus present in each area (Koiwaya 2007). Although Koiwaya suggested that Sibataniozephyrus lijinae Hsu, 1995 from mainland China might utilize the same Fagus species as S. kuafui Hsu & Lin, 1994 from Taiwan, there is still no evidence to support this idea.

We would like to express our sincere thanks to Mr Yasunori Kishida (Tokyo, Japan), Mr Keitaro Eda (Shizuoka, Japan), Mr Hao Huang (Qingdao, Shandong, PR China), Mr Yu-fei Li (Xi’an Jiaotong University, Shaanxi, PR China), Dr Hong-liang Shi (Beijing Forestry University, Beijing, PR China), Mr Di Lu (Xidian University, Shaanxi, PR China), Mr Wen-hao Sun (Northwest Agricultural & Forestry University, Shaanxi, PR China), and Mr Shu-qin Ji (Shenzhen Institutes of Advanced Technology, Chinese Academy of Science, Guangdong, PR China) for providing valuable material and field photographs, to Mr Zhen-fu Huang and Yu-ke Han (SCAU, Guangzhou, Guangdong, PR China) for improving the manuscript and providing valued advice. We are also grateful to Prof Ming-yi Tian, Ms Meng-zhen Chen and Zi-jun Ma (SCAU, Guangzhou, PR China) for helping with the genitalia photographs.