Taxonomic study describes Digitivalva bella, a new moth species from Japan

A taxonomic study has described Digitivalva bella sp. nov., a moth from Japan distinguished by bright orange forewings bearing silvery-white stripes, characteristic male and female genitalia, and pupation beneath the epidermis of its host plant. The species belongs to Digitivalva, one of five genera in Acrolepiinae, a subfamily of Glyphipterigidae also known as false diamondback moths. The subfamily contains approximately 100 described species outside the Australian Region, with about half distributed in the Palearctic.

Its larvae are plant feeders and are mostly leaf miners, although some also bore into seeds, stems and flower buds. Before this study, 15 Acrolepiinae species—13 described and two unidentified—had been recorded from Japan in three genera. Three named Digitivalva species and one unidentified form had previously been reported from Japan.

A 2018 report described the unidentified form as a leaf miner in Campanula punctata on the Izu Peninsula in Shizuoka Prefecture. During the present study, field research was conducted on the peninsula in April 2021, late March and April 2022, September 2022 and April 2023. Larvae were collected from host plants and reared in plastic cases at 24–28 °C until adult emergence.

Identifying the host was difficult when the plant was in its spring rosette stage. A return visit in early September 2022 allowed the researchers to examine its flowers and establish that the host was not Campanula punctata but Carpesium divaricatum , a member of the Asteraceae. Labels on historical specimens collected near Mount Hikosan in Fukuoka Prefecture also described the moth as a leaf miner of Carpesium divaricatum , supporting the corrected host identification.

Adult morphology, wing venation, male and female genitalia and pupal structure formed the basis of the taxonomic description. External features were observed with a stereomicroscope. For genitalic examination, abdomens were detached from dried specimens, macerated in 10% potassium hydroxide for 5–10 minutes in a heated water bath, neutralised in acetic acid and stained with Chlorazol Black E or mercurochrome.

The dissected genitalia were then dehydrated, mounted in Euparal and examined microscopically. The new species is readily distinguished from other Digitivalva species by its bright orange forewings with silvery-white stripes. Among the examined material, male D. bella had wingspans of 9.0–12.0 mm in 36 paratypes, while the holotype measured 11.5 mm; female paratypes measured 8.0–12.0 mm.

The sexes were not markedly dimorphic, although females were sometimes darker. The forewing pattern included four broad, black-edged silvery-white stripes and black triangular dashes near the anal and apical margins. Male genitalia provide additional diagnostic characters, including a single vertical split at the apex of each costal arm of the valva and a C-shaped valva.

The female genitalia have an ovally rounded ostium bursae, distinguishing the species from D. arnicella , which has a triangular ostium bursae and lacks a signum. The specific name bella is the female form of the Latin adjective bellus , meaning “beautiful,” and refers to the striking orange-and-silvery-white forewing pattern. Larvae of D. bella mine inside host leaves, producing broad linear to blotch mines.

Mature larvae weave cocoons beneath the leaf epidermis near the petiole. Unlike the usual single-layer, mesh-like Acrolepiinae cocoons, these cocoons have a rough outer layer of thick silk and a smooth inner layer of fine silk. Pupae measured 6.5–7.5 mm long and approximately 1.5 mm wide, with a small triangular vertex process interpreted as a cocoon cutter.

Under laboratory conditions, the mean pupal period was 14.5 days for 33 pupae. The study documents D. bella from Hokkaido, Honshu, Shikoku and Kyushu, with Carpesium divaricatum identified as its host plant. Adults occur at least twice annually, although timing varies by location: the Izu Peninsula population emerged in April, whereas adults in Fukuoka emerged from July to August.

Some adults collected during the day were resting on flowers of Eupatorium chinense var. simpliciforium . The authors reported that under-epidermal pupation had not previously been documented for Acrolepiinae in Japan, while a similar habit had been described for D. arnicella in Europe. Shared morphological and biological features may indicate a closer relationship between those two species, but the precise evolutionary position of D. bella requires further research.

Subject of Research: Taxonomic description and life history of the newly described Japanese moth Digitivalva bella

Article Title: A remarkable new species of the genus Digitivalva Gaedike, 1970 ( Lepidoptera , Glyphipterigidae , Acrolepiinae ) from Japan

Article References: Zhang, X., Yagi, S., & Hirowatari, T. (2024). A remarkable new species of the genus Digitivalva Gaedike, 1970 (Lepidoptera, Glyphipterigidae, Acrolepiinae) from Japan. Nota Lepidopterologica, 47, 187-199. https://doi.org/10.3897/nl.47.130063

Image Credits: AI Generated

DOI: 10.3897/nl.47.130063

Keywords: Digitivalva bella, new species, moth taxonomy, Lepidoptera, Glyphipterigidae, Acrolepiinae, morphological description, leaf mining, pupal morphology, Japan, remarkable, species