Flies infesting Kotagiri, Coonoor are not harmful ‘black flies’: researchers

Flies that have swarmed parts of Kotagiri and Coonoor have been identified as ‘mosquito fungi’ by wildlife biologists | Photo credit: Special arrangement

A team of wildlife biologists investigated recent reports of fly swarming in parts of Kotagiri and Coonoor towns in the Nilgiris to determine whether the flies seen in these areas were harmful to humans. Scientists have concluded that the flies belong to the family known as Sciaridae, commonly known as black mosquitoes, and do not pose a threat to human health.

N. Moinudheen, an independent wildlife biologist working in The Nilgiris, told The Hindu that media reports had wrongly identified the flies in Kotagiri and Coonoor as “black flies” or buffalo mosquitoes, which are known to adversely affect human health in certain parts of the world.

What are black-winged fungus gnats?

“This fly seen in Coonoor and Kotagiri belongs to the Sciaridae family, commonly known as black-winged fungus gnats. They are often found in moist soil and greenhouses, with the highest egg-laying activity during the monsoon and summer seasons. Their larvae feed on roots and can damage young seedlings in commercial crops.”

These flies pose no threat to humans; they do not bite, sting or inject venom. Their life cycle lasts 21 to 28 days, during which they lay 100 to 200 tiny eggs. They usually lay their eggs in moist soil and decaying organic matter. Adult flies feed primarily on nectar and are harmless; however, their larvae inhabit moist organic-rich compost. These larvae are commonly found in mushrooms, decomposing organic matter, commercial mushroom farms and greenhouse plants. They are a notorious and costly pest in the commercial mushroom industry,” they said.

Researchers, wildlife conservationists and NGOs including the Wildlife and Nature Conservation Trust (WNCT) and Ongil Nature Trust participated in the investigation, which included members Arockianathan Samson, A. Abinesh, Azad Kamil, Sadiq Ali, N. Moinudheen, Mohammed Shahir and E. Vignesh, who set out to identify fly species at lower altitudes in Co Ngoilris and E. Vignesh. Kotagiri.

They said the flies have natural predators in burrowing beetles that feed on mosquito larvae, but that the beetles are declining in areas due to heavy pesticide use, while predatory mites also prey on the flies.

The team visited one of the affected areas on Monday (July 20, 2026) in Selas near Coonoor. They said they noticed that flies were more prevalent around water sources and although the local civic organization was conducting fumigation operations, they proved ineffective as the flies kept coming back.

Affected businesses

Since last week, local residents around Coonoor and Kotagiri towns have complained of fly infestation, saying the flies are causing irritation to their eyes, while economic activity, especially in restaurants and eateries, has also been affected.

Control measures

Scientists have recommended measures that can be taken to control the infestation. “These flies do not pose a direct threat to humans, although they are common this season. To control them, identify breeding sources: look for moist or damp areas that encourage mold growth, moist substrates, water seepage in walls and cavities.

Infestations often come from contaminated potting soil. Sciariids multiply rapidly, making complete eradication difficult,” they said.

They also appealed to the public not to spread panic over flies and urged scientific intervention by local civic bodies and district administration to control the problem.

Published – 21 Jul 2026 13:10 IST