Six butterfly species never before recorded in India have been discovered in Arunachal Pradesh’s Siang Valley.
The study reveals ecological links between Tibet’s Yarlung Tsangpo and India’s Brahmaputra basin.
The discovery emerged from a camera-trapping project in the Litin Community Conserved Area.
Local villagers have protected their ancestral forests through community-led conservation.
Researchers warn that hydropower projects and climate change threaten the region’s unique biodiversity.
In the quiet folds of Arunachal Pradesh’s Siang Valley, where clouds drift low over forests of oak and rhododendron, a group of villagers and researchers have made discoveries that deepen the mystery of India’s eastern Himalayas.
During recent biodiversity surveys in Simong village, Upper Siang district, six butterfly species never before recorded in India were documented. The findings, published in Entomon Journal, reveal a rare ecological bridge between the Brahmaputra River in Tibet — known there as the Yarlung Tsangpo — and the forests on its southern bank in Arunachal Pradesh.
Among the six are species as lyrical as their colours: the Litin Onyx (Horaga takanamii), Tibetan Junglequeen (Stichophthalma neumogeni renqingduojiei), and Tibetan Duke (Euthalia zhaxidunzhui). All were previously known only from Laos, Vietnam and south-eastern Tibet.
“The discovery is significant because the existence of the Metok element of butterflies from the upper Brahmaputra in Tibet within Siang Valley was never highlighted before,” said Monsoon Jyoti Gogoi, senior coordinator at Ashoka Trust for Research in Ecology and the Environment (ATREE) and lead author of the study.
The discovery was serendipitous. The team was conducting a camera-trap survey to document mammals in the Litin Community Conserved Area (CCA), about 11 kilometres from Yingkiong, when they began spotting unusual butterflies along their routes.
“Balancing camera-trap work and butterfly documentation was difficult,” Gogoi recalled. “Our surveys were purely opportunistic while trekking to set up traps, but even so, we found species earlier known only from Tibet and Southeast Asia.”
The Brahmaputra, he explained, appears to act as an evolutionary corridor between the Sino-Himalayan and Indo-Himalayan regions. “These findings help us understand the species assemblages shared between India and Tibet due to the river’s course.”
For Gogoi, three species stood out — the Litin Onyx, Tibetan Junglequeen and Tibetan Duke — for their unexpected presence so far west of their known range. “It was astonishing to see them here,” he said. “Some were thought to exist only in Tibet or Southeast Asia.”
If the scientific discovery showcases Siang Valley’s biodiversity, it also reveals the positive impacts of local conservation. The Litin clan of Simong village has protected its ancestral forest through community stewardship.
“We decided to set aside Litin forest as a community conserved area to protect our biodiversity and traditional heritage,” said Agur Litin, a Green Hub fellow and member of the Litin CCA. “When hunting and logging increased, we realised we had to act before it was too late.”
Village decisions are made collectively through a committee representing every household. Although the CCA is only a few years old, Agur has already seen a change — not just in wildlife, but in attitudes.
“There’s a new awareness,” he said. “People feel more responsible now. And knowing that our forest is home to rare species gives us pride. It shows that our traditional ways of protecting land have value even beyond our village.”
To honour the community’s efforts, the researchers gave Horaga takanamii a common name in their honour — the Litin Onyx. “We took the opportunity to name it after the Litin clan for their dedication to conservation,” said Gogoi.
Agur hopes the Litin CCA will inspire others. “It stands as the lone example of community-led conservation in Siang Valley. It can encourage other villages to conserve their ancestral forests through similar models.”
Fragile landscapes, uncertain futures
The slopes above Simong are part of one of India’s least-studied biodiversity regions, but they face growing pressure from timber extraction and expanding cultivation. Larger threats loom in the form of hydropower projects along the Siang River, including the long-proposed Siang dam that could submerge parts of the valley.
“The areas adjoining Yingkiong and Simong face risks from habitat loss and climate change,” Gogoi warned. “Without active conservation, many species could vanish before we even know they exist.”
He believes more systematic surveys could establish Arunachal Pradesh as “the number one butterfly hotspot in the Oriental region.”
Upstream, China has already built several dams on the tributaries of the Yarlung Tsangpo, including the Zangmu Dam. It has reportedly begun constructing a colossal hydropower project on the river’s Great Bend, where it plunges nearly 2,000 metres before entering India.
From India’s perspective, any alteration of river flows upstream could affect riparian ecosystems, the timing of monsoon floods, and species migration corridors linking the Tibetan plateau with the Indo-Himalayan region.
In response, New Delhi is accelerating its own hydropower plans, a strategy seen both as a hedge against upstream control and as recognition of the Brahmaputra system’s fragile ecology.
Arunachal Pradesh Chief Minister Pema Khandu has described China’s planned dam as a “ticking water bomb”, calling for a domestic project that could act as a buffer against sudden releases of water from across the border.
The region, one of the planet’s deepest and most rugged river gorges, is also a hotspot of Himalayan biodiversity and seismic activity. Large infrastructure here could disrupt sediment flows, trigger landslides, and alter the hydrology that sustains forests and floodplains far downstream.
In the Adi community’s oral traditions, butterflies flit between the natural and the mystical. They appear in miri ponung folk songs as tumi lotmo — beings of wisdom and leadership, said to have once guided mithuns to salt springs deep in the forest. Such stories, while poetic, hold truths that science is now rediscovering — that Arunachal’s forests, long tended by its people, form connections that transcend borders.
As dusk falls over Siang Valley, the forest glows with the soft movement of wings — reminders of a fragile web that binds Tibet’s high mountains to India’s rain-drenched hills, and of a village that guards the bridge between them.
Butterfly awareness has soared in Arunachal Pradesh in recent years, with local festivals becoming hubs of citizen science. In July this year at the High-Altitude Mechukha Butterfly and Biodiversity Meet, in Mechuka, 107 species were recorded including the Metok green sapphire (Heliophorus gloria) and the Medog tufted ace (Sebastonyma medoensis).
At Ziro, the butterfly meet held its 12th edition this year. More recently at the second edition of Wakro Butterfly Meet, 235 species of butterflies that included 35 rare and uncommon species were recorded.
“These events have helped students and youth understand why biodiversity matters,” said Minom Pertin, a butterfly enthusiast and junior engineer with the state Department of Power, associated with the Society for Education and Environmental Development (SEED). “Many park checklists have been updated as a result.”
He said such gatherings should extend beyond protected areas to community lands. “They create a bridge between experts and local communities, giving everyone a chance to sit together and talk about nature, science, and traditional knowledge.”
“Documentation of six new butterfly species for India from Arunachal is very positive news for both the state and the country,” Pertin added. “It shows how biologically important our forests are, and why stronger protection policies are needed.”
While he welcomed government support for butterfly meets, he said implementation often lagged. “Some authorities limit the role of NGOs or use funds on a very small scale. Support must be implemented in true spirit,” he said.