Hidden Pollinators of the Gangetic Plains: ZSI Scientists Discover Two New Hoverfly Species After More Than a Century
By Suman Munshi
Kolkata, June 3: In a remarkable breakthrough for Indian biodiversity research, scientists from the Zoological Survey of India (ZSI) have identified two previously unknown species of hoverflies from the Gangetic Plains of West Bengal, marking the first major addition to India’s known Eristalinus hoverfly fauna in over 100 years.
The newly discovered species, named Eristalinus sapphirinus and Eristalinus brunettii, were documented in a study published in the prestigious European Journal of Taxonomy. The research was carried out by ZSI scientists Bristi Roy, Oishik Kar, and Dr. Jayita Sengupta, under the guidance of Dr. Dhriti Banerjee, Director of ZSI, and Dr. Atanu Naskar, Officer-in-Charge of the Diptera Section at ZSI, Kolkata.
Century-Old Scientific Gap Filled
Hoverflies belonging to the family Syrphidae play a crucial role in maintaining ecological balance by pollinating flowering plants and supporting biodiversity. Despite their ecological importance, the Eristalinus group had received little scientific attention in India since the early 20th century, with the last significant taxonomic contribution recorded in 1923.
To uncover this hidden diversity, researchers examined hoverfly specimens collected from multiple districts across West Bengal between 2022 and 2025. Using a combination of detailed morphological studies and advanced mitochondrial COI DNA barcoding techniques, the team confirmed that the specimens represented two species previously unknown to science.
The species Eristalinus sapphirinus derives its name from its distinctive sapphire-blue metallic appearance, while Eristalinus brunettii honors renowned entomologist Enrico Adelelmo Brunetti for his pioneering contributions to the study of Indian flies.
Advanced Science Reveals Hidden Biodiversity
The study employed an integrative taxonomic approach that combined traditional morphology with modern genetic tools. Researchers analyzed COI DNA barcodes using four internationally recognized species-delimitation methods—ABGD, GMYC, ASAP, and PTP—to establish the uniqueness of the newly discovered species.
According to the researchers, this approach helped reveal species that are often difficult to distinguish through appearance alone.
Small Insects, Big Ecological Impact
Members of the Eristalinus genus perform critical ecological functions throughout their life cycle.
As adults, these hoverflies act as effective pollinators, visiting flowers and supporting both wild vegetation and agricultural crops. During their larval stage, commonly known as “rat-tailed maggots,” they inhabit aquatic environments where they help break down organic matter and recycle nutrients, contributing to ecosystem health.
The findings also demonstrate that significant biodiversity continues to thrive within human-modified landscapes such as the Gangetic Plains, challenging the assumption that important discoveries can only be made in remote forests or protected reserves.
ZSI Leadership Highlights Importance of Discovery
Dr. Dhriti Banerjee, Director of the Zoological Survey of India, emphasized the broader significance of the finding.
“The discovery reminds us that biodiversity does not survive only in remote forests. Even highly human-modified landscapes like the Gangetic Plains continue to harbour unknown life forms. Nature still has countless stories waiting to be discovered.”
Dr. Atanu Naskar, Officer-in-Charge of the Diptera Section at ZSI Kolkata, highlighted the role of modern scientific tools in resolving taxonomic challenges.
“Many hoverfly species are remarkably similar in appearance, making accurate identification challenging. By integrating traditional morphological taxonomy with DNA barcoding and modern species-delimitation approaches, we were able to confidently establish the distinct identity of these two new species.”
Lead researcher Bristi Roy underscored the ecological importance of pollinating insects and the need for continued biodiversity documentation.
“Pollinating insects form the foundation of healthy ecosystems, and hoverflies are among their significant yet least recognized members. The discovery of these two new species after a century highlights how much of our insect biodiversity remains undocumented, even in landscapes we encounter every day.”
A Reminder of Nature’s Unexplored Wealth
The discovery of Eristalinus sapphirinus and Eristalinus brunettii serves as a powerful reminder that India’s biodiversity remains far from fully documented. Even in densely populated and extensively modified regions such as the Gangetic Plains, scientists continue to uncover species new to science, underscoring the importance of sustained research, conservation efforts, and biodiversity monitoring.
