Rare mayfly insect species thought to be extinct rediscovered in Thailand after 20 years

Behningia baei McCafferty & Jacobus, 2006. A. Fine sand grains from the microhabitat. B. Live specimen, dorsal view. C. Live specimen, sand burrowing behaviour. D. Live specimen, ventral view. (Image: checklist)

Two tiny mayfly nymphs, almost lost to time, have surfaced once again. Researchers in northern Thailand spotted the elusive Behningia baei during a river survey in December 2024, ending a 22-year silence.

The rare insect, first described in 2006, had vanished from records. Despite many expeditions, it had not been seen since its discovery 250 miles to the south. That changed when a team led by Sedtawut Kwanboon and Boonsatien Boonsoong found two juveniles hiding in the Mae Chaem River’s fine sand.

A Life Hidden Beneath the Surface

Unlike many insect studies that track adults, the team used kick nets. They stirred riverbeds to find buried nymphs—safer and easier to sample. The tiny arthropods, measuring just 1–3mm, were examined under a microscope. Every feature matched the original 2006 description of B. baei.

These mayflies spend much of their lives under sand, away from predators and sunlight. Being blind and pale, they show typical adaptations to cave-like river habitats. Despite their size, they are crucial to river ecosystems—both as grazers and prey.

Mayflies help shift nutrients and oxygenate riverbeds by digging. They are also sensitive to pollution, making them reliable indicators of clean water. Their presence confirmed that the Mae Chaem stretch still carries healthy, oxygen-rich flow.

A Wider Reach Than Previously Known

This rediscovery pushes B. baei's known range 250 miles north. The site, 1,350 feet above sea level, suggests the species can thrive in cooler upland rivers. With only one other Behningia species previously found nearby, the discovery highlights the area's conservation value.

Adult mayflies live for just hours—some for mere minutes—making sightings rare. By studying juveniles, researchers avoid disrupting breeding cycles and gather more reliable data. This approach also sets an ethical standard for fragile populations.

Conservation, Community, and the Path Ahead

The team plans DNA barcoding to confirm identity and rule out hidden sibling species. More surveys in nearby streams are on the way before monsoon rains cloud the rivers.

To ensure the research continues, local students are being trained to use kick nets. These small steps could lead to large gains in conservation awareness and data collection.

River sandbars, often missed in environmental policy, hold unique lifeforms. Even slight changes in the sediment can threaten species like B. baei. Protecting these habitats means more than fighting pollution—it means keeping riverbeds stable and undisturbed.

The rediscovery isn’t a conclusion. Instead, it marks a renewed effort to understand a fragile insect with a fleeting adult life. For a species buried in silence for 20 years, its return is a quiet triumph worth listening to.

The findings have been published in Check List.