Research report: Xenotorodor stygioxanthus gen. nov., sp. nov. ( Lepidoptera , Lecithoceridae , Torodorinae ), described from an established population in Spain with discussion of taxonomic placement

Deep in the scrubland near Tarifa, on the Spanish side of the Strait of Gibraltar, a small black-and-yellow moth has been quietly flying around mercury vapour lights since at least May 2020. When researchers finally sat down to identify it, they discovered something remarkable: the insect belonged to a family of micromoths almost entirely absent from Europe, matched no known genus, and carried DNA barcodes more than 9 percent divergent from any cleanly sequenced lepidopteran on record. The family Lecithoceridae is a poorly known group of small moths concentrated in the Oriental tropics, Australia and the Afrotropical region.

Only 64 species, roughly 4.5 percent of the global total, are known from the Palaearctic, and just ten of those have been reported from Europe, all belonging to the subfamilies Ceuthomadarinae and Lecithocerinae. Five of the European species had previously been recorded from Spain. The new moth fits none of them.

Its discovery began when Dave Grundy found the first specimen at mercury vapour light at the Centro Internacional de Migración de Aves research facility in Tarifa, Cádiz Province, on 18 May 2020. Since then, 93 adult specimens have been recorded at or near the research centre, with two more found at Huerta Grande, Pelayo, roughly ten kilometres away. Identifying the stranger proved anything but straightforward.

European lecithocerid taxa were quickly ruled out on morphological grounds, but a search of online images revealed striking similarities in general appearance and even resting posture to the tropical genera Sisyrodonta and Protolychnis, particularly in the thickened antennae and wing pattern. The arrival of a comprehensive global review of the subfamily Torodorinae, together with an earlier treatment of the subfamily Crocanthinae, allowed the team to check every plausible generic affiliation morphologically. To go further, they DNA barcoded three specimens and analysed essentially all publicly available DNA sequences of Lecithoceridae.

The molecular work was extensive. DNA was extracted from single hindlegs of three male specimens and standard Sanger PCR was used to amplify the COI-5P barcode region, with sequencing carried out using third-generation technology: fragments were tagged with Illumina indexes, pooled onto a single-use 200-pore Oxford Nanopore Flongle flow cell, and run for 72 hours on a benchtop GridION machine. Bioinformatic demultiplexing retrieved tagged barcode fragments for each sample, achieving a minimum coverage of 25 high-fidelity fragments per 658-base-pair sequence.

The sequences are now public on the BOLD database and GenBank, under the Barcode Index Number BOLD:AFA0579. The new moth's barcodes are more than 9.2 percent pairwise divergent from any hitherto cleanly sequenced Lepidoptera taxon, and more than 10.1 percent divergent from its nearest taxonomically identified neighbours in both Neighbor Joining and maximum likelihood trees. The closest identified lecithocerid, Thubana exoema from Sri Lanka, sits 9.2 to 9.38 percent away.

A local BLAST search against 429 Barcode Index Number representatives of Lecithoceridae downloaded from BOLD found the nearest hits – a Malaysian species and a Pakistani one – still roughly 9.6 to 10 percent divergent. The team also hunted for molecular signatures shared across lineages. Examining the amino acid translation of the barcode region, they found that the 161st complete codon carries the amino acid Asparagine rather than the Serine more usual in the superfamily Gelechioidea.

Among 429 lecithocerid BINs, 91.8 percent showed Asparagine at this position, compared with under 1 percent of related Autostichidae and 2.5 percent of Xyloryctidae. The new moth carries the Asparagine state, which the authors interpret as a ground-plan synapomorphy of the family Lecithoceridae – a shared derived character confirming its family placement even as its genus remained elusive. Phylogenetic analyses reinforced the picture.

Morphologically, the moth shows the thorn-like uncus and absence of a bridge between tegumen and valva that define Torodorinae, despite its unusually reduced gnathos – a feature that initially suggested Crocanthinae, since that subfamily is defined by a reduced or absent gnathos. But the new moth lacks nearly every other Crocanthinae hallmark: its labial palps are not dimorphic, its forewings lack the postmedian fascia, its wing venation differs substantially, and its appearance matches nothing described from that largely New Guinean and Australian group. The insect itself is distinctive.

The forewings are black with a purplish sheen, crossed by a narrow yellow bar before the midpoint and marked with a yellow costal spot at three-quarters length; the antennae and labial palps are yellow, and in the male the antenna is thickened with rings of large yellow scales projecting outward from each flagellomere. The wingspan is a modest 13 to 15 millimetres. The genus name Xenotorodor draws on the Greek xenos, meaning stranger or outsider – a nod both to the unusual combination of features for a torodorine and to the subfamily's substantial geographic extension – while stygioxanthus combines the Greek for extremely dark and yellow, referencing the blackish forewings marked with yellow.

Since 2020 the species has been recorded nearly 100 times, all from a small patchwork of Mediterranean scrub, grazed pasture, wild olive groves and Eucalyptus plantations near Tarifa, with adults flying in May, June, August, September and November and principal emergences in late May-June and August. Both sexes come to mercury vapour light in the two hours after darkness, and at rest the moth holds its wings flat with antennae projected upward and sideways in an alert posture. The life history and early stages remain unknown; leaf-litter sampling in May 2022 proved unsuccessful.

Where the moth came from is equally unresolved. It could be a long-resident but previously overlooked native, though the authors note the taxon is distinctive, evidently common where it occurs, and unlikely to have escaped notice in a reasonably well-studied Spanish microlepidoptera fauna. Alternatively, it may be a recent arrival from North Africa, where warming conditions are pushing species northward across the strait – a route already taken by several other species recorded around Tarifa.

A third possibility, introduction via Eucalyptus plantations from Australia, seems less likely given that the moth is not closely related to any barcoded Australian lecithocerid genus. Beyond the novelty itself, the study exposes gaps in current knowledge. The authors conclude that existing data are insufficient to demonstrate that Torodorinae and Crocanthinae are genuinely separate clades, and that the morphological synapomorphies supporting the family and its two subfamilies need refinement – an expanded phylogenomic dataset is clearly needed.

Torodorinae is widespread across the palaeotropics, yet the origin of Xenotorodor cannot be narrowed further. What is certain is that a lineage new to Europe is now established on Spanish soil, and that further field and taxonomic work in southern Spain and adjacent North Africa is likely to yield more surprises about the region's changing fauna.

Subject of Research: A new genus and species of lecithocerid moth from southern Spain representing the first European record of the subfamily Torodorinae

Article Title:  Xenotorodor stygioxanthus gen. nov., sp. nov. ( Lepidoptera , Lecithoceridae , Torodorinae ), described from an established population in Spain with discussion of taxonomic placement

Article References: Sterling, M. J., Lees, D. C., & Grundy, D. (2023). Xenotorodor stygioxanthus gen. nov., sp. nov. (Lepidoptera, Lecithoceridae, Torodorinae), described from an established population in Spain with discussion of taxonomic placement. Nota Lepidopterologica, 46, 103-123. https://doi.org/10.3897/nl.46.101457

Image Credits: AI Generated

DOI: 10.3897/nl.46.101457

Keywords: Lecithoceridae, Torodorinae, new species, new genus, Xenotorodor stygioxanthus, DNA barcoding, Spain, Tarifa, Lepidoptera, taxonomy, phylogenetics, micromoths