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Hagenella clathrata 

Hagenella clathrata - Window-winged Cadd

A rare caddis fly that lives in a small number of the remaining raised bogs and heathlands in the UK.

  • Rarity: In the south of England it is only found in 4 sites.

  • Causes of decline: The drying out of their boggy habitat, the encroachment of trees into their habitat, wildfires, and the opening of tussock habitat by livestock trampling the ground.

The Window-winged Caddis Fly is one of the rarest insects in the UK. In the south of England, it is only found at Chobham Common, Whitmoor Common and Frensham Common in Surrey and Ancells Farm and Foxlease Meadows in Hampshire.

While there appears to be a strong population remaining at Whitmoor Common, sadly, in recent years, surveys have failed to find the caddis fly at Chobham Common. This suggests that the population is struggling or may even have disappeared.

This is likely to be a result of scrub encroachment. This is a major threat to Window-winged Caddis Flies, as it leads to the drying out of the boggy habitats that the caddis fly depends on.

Sadly, this species is also vanishing from almost all of its European range, as its bog habitats are exploited.

Over the last few years, we have been working to train volunteers to survey for this species in both Surrey and Hampshire. Our volunteers have recorded lots of caddis flies at Whitmoor Common which is a really positive finding. However, at Chobham Common we have not had any definitive records and our volunteers reported a decline in the quality of the habitat. 

We need to ensure that any individuals remaining on Chobham have the best chance of survival so have been working to encourage Surrey Wildlife Trust, who manage the site, to undertake habitat work for this species. They have recently undertaken significant improvement works and so hopefully this will have very positive impacts for the species.

In addition, in the last couple of years, Window-winged Caddis Flies have been discovered at two new sites: Ancells Farm and Foxlease Meadows in Hampshire, and Frensham Common in Surrey. 

Recent surveys by our volunteers have demonstrated that the population at Ancells Farm and Foxlease Meadows is an established breeding population, which is fantastic news for the species. It may well be that there are other undiscovered populations in Surrey and Hampshire, and we hope that by training a network of volunteers we will be able to find them. 

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