Guwahati: A tiny moth collected near Hollongapar Gibbon Sanctuary in Assam has turned out to be a species previously unknown to science, adding another entry to the biodiversity records of Northeast India.

The newly described species, Apethistis minapaksha, was collected during a field survey near Mariani. Its identification brings the number of known species in the genus to 19 worldwide.

The moth, measuring barely 11 mm across its wings, was identified as a new species by Kishore Chandra Sahoo, Scientist, ICAR-Indian Agricultural Research Institute (IARI), Assam. The findings were published in the latest issue of the taxonomic journal Zootaxa on Monday.

The discovery emerged from a closer examination of specimens that might otherwise have been overlooked because of their small size and relatively inconspicuous appearance.

The new species belongs to the genus Apethistis, a group of micro-moths in the family Autostichidae. Before this discovery, 18 species of the genus were recognised worldwide, including eight in India.

The description of A. minapaksha raises those numbers to 19 globally and nine in India.

A distinguishing feature hidden from the naked eye

At first glance, the moth does not appear particularly different from other members of its genus. Its wings are predominantly soil brown, with small dark spots along the outer edges. The wingspan ranges from 10.5 to 11.5 mm.

The distinction, however, lies in a feature that cannot be seen without examining the insect under a microscope.

The researchers found that the male moth has a distinctive fin-shaped process on its reproductive structure, known as the valva. This feature helps distinguish it from closely related species.

The new species bears some resemblance to Apethistis dentata, described from China in 2017. Both have a pointed process at the tip of the valva. But A. minapaksha has an additional fin-shaped dorsal process near the tip, which sets it apart.

The name reflects this feature. Derived from the Sanskrit words m?na, meaning fish, and pak?a, meaning fin or wing, minapaksha refers to the fin-like structure.

The female of the species has not yet been identified.

What the collection revealed

The study was based on five male specimens — one designated as the holotype, the reference specimen for the species, and four additional specimens classified as paratypes.

The researchers examined the moths under a stereo zoom microscope and prepared the male genitalia for detailed study. They also documented the wing venation, another important feature used in identifying and classifying micro-moths.

The specimens have been deposited in the reference collection of ICAR-IARI, Assam, allowing other researchers to examine them in future studies.

The paper was authored by Sahoo, with Abhijith K. P. of ICAR-IARI, Assam, assisting in the collection. Jayanta Jyoti Sarmah provided support as a local guide during the field survey.

A closer look at Assam’s insect diversity

The discovery adds to the growing body of taxonomic work documenting insect diversity in Northeast India.

Moths are among the most diverse groups of insects, but many smaller species remain difficult to identify. Their classification often depends on subtle differences in wing structure, venation and anatomy that require specialised examination.

The study also points to areas where the classification of Apethistis itself remains unsettled. The authors note that the placement of several species in the genus needs further examination, including detailed study of specimens preserved in museum collections.

For Assam, the finding highlights the need for further scientific exploration, as many small and previously undocumented species still awaits discovery.