Rahul SomvanshiThe Surprising Comeback: Limnephilus Pati Interactive Guide
After being presumed extinct in Britain since 2016, the Limnephilus pati caddisfly has been rediscovered at Cors Goch wetland in Anglesey, Wales. Explore this remarkable insect through our interactive guide.
The Limnephilus Pati Caddisfly
Identification Features
Habitat Requirements
Did you know? Britain is home to approximately 200 different caddisfly species, but Limnephilus pati is one of the rarest and most habitat-sensitive.
The Remarkable Life Cycle
Click each stage to learn more about the caddisfly’s development:
Eggs
Larva
Pupa
Adult
Egg Stage
Female caddisflies deposit egg masses in or near water. The eggs are typically enclosed in a jelly-like substance that helps protect them until they hatch. This stage lasts approximately 2-3 weeks, depending on water temperature and conditions.
Larval Stage – “The Case-Builder”
This is the longest stage in the caddisfly’s life. The aquatic larvae are known for building protective cases using silk they produce, combined with materials from their environment like sand, small stones, plant fragments, and seeds. These cases provide camouflage and protection while they develop. The larvae live underwater among dense vegetation roots and feed on plant material and organic debris. This stage can last several months to a year.
Pupal Stage
When ready to pupate, the larva attaches its case to a submerged object and seals both ends, leaving small holes for water circulation. Inside this protective chamber, the transformation into an adult begins. The pupal stage typically lasts 2-3 weeks.
Adult Stage
The adult caddisfly emerges from the water and takes flight. Adults have hairy wings rather than the scales found on moths. They primarily fly from spring to early August. The adult stage is relatively short, lasting just a few weeks. During this time, their main purpose is to mate and lay eggs for the next generation. Adults are most active at dusk and dawn.
The Three UK Locations
Since being presumed extinct in 2016, Limnephilus pati has been found in just three locations across Britain. Click on the map markers to learn more about each site:
Location Information
Click on a map marker to see details about each discovery site.
Why This Discovery Matters
Water Quality Indicator: The presence of Limnephilus pati signals exceptionally clean, calcium-rich water – a rare condition in modern wetlands. Their sensitivity makes them excellent bioindicators of ecosystem health.
Ecological Value
Conservation Implications
“This incredible discovery shows why consistent surveying is such an important element of conservation work.”
— Clare Sampson, Natur am Byth project manager for RSPB
A small moth-like insect, thought extinct in Britain since 2016, has been rediscovered at a wetland site in Wales. Surveys at Cors Goch on Anglesey turned up Limnephilus pati, a caddisfly species that needs very clean, calcium-rich water to survive.
Natur am Byth (NaB), Wales’ flagship species recovery programme, wasn’t even looking for this insect when they found it. Their team set up light traps at Cors Goch during July and August 2025, hoping to catch another rare species called Limnephilus tauricus. Instead, they caught something even more unexpected.
When experts confirmed the identity of the insect, it marked Cors Goch as just the third place in Britain where this caddisfly has been found since it was presumed extinct in 2016. The only other sites are Market Weston Fen in Suffolk and Eochar in South Uist, Scotland.
“Anglesey is the only known place in Wales where you can find this unique caddisfly,” said Clare Sampson, Natur am Byth project manager for RSPB. “It was a delight to find it at Cors Goch along with other species that indicate clean water and a rich habitat.”
This bug is picky about where it lives. It requires very clean, calcium-rich water – exactly what’s found at Cors Goch, a shallow valley fen where some peat deposits reach over 10 meters deep in places. The North Wales Wildlife Trust manages this site, which became their first nature reserve back in 1967.
Caddisflies are nature’s water quality monitors. The adults look like small moths with hairy wings instead of scales. Their larvae live underwater, building protective cases from sand, bits of plants, and other materials bound with silk.
“Caddisflies survive by being masters of disguise,” Sampson explained. “The brown adults blend into vegetation, while the larvae live inside cases they camouflage with stems, sand and seeds.”
With around 199 caddisfly species in Britain, Limnephilus pati stands out for its rarity and specific habitat needs. The wetlands where it lives face growing threats from drying out and agricultural intensification. Adults fly from spring to early August, while their larvae develop underwater among dense plant roots.
Cors Goch is home to other rare species that need similar clean-water conditions, including the Clubbed General Soldier Fly (Stratiomys chamaeleon) and Dwarf Stonewort (Nitella tenuissima), both NaB target species.
This find shows the value of regular wildlife surveys. “This incredible discovery shows why consistent surveying is such an important element of conservation work,” noted Sampson.
The Natur am Byth programme, funded by the National Lottery Heritage Fund, works across Wales to improve habitats and minimize threats to 67 target species. Their systematic approach helps spot both known rarities and unexpected survivors like this once-missing caddisfly.
The discovery at Cors Goch involved the partnership of RSPB and North Wales Wildlife Trust in their ongoing efforts to monitor and protect special habitats across Wales.
