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 2 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 and Whitmoor Common.

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, which is a major threat to Window-winged Caddis Flies, as it leads to the drying out of the boggy habitats that it depends on.

Window-winged Caddis Flies in the south of England Species Report 2018

The Window-winged Caddis Fly, Hagenella clathrata, is an extremely rare species. It only survives in a handful of sites in England and is also vanishing almost everywhere in Europe as its bog habitats are exploited.

This project aimed to survey two of the key sites in England for these species, Chobham Common and Whitmoor Common. It also aimed to train a number of volunteers in survey methods, so that they can continue surveying for this species in the future.

We spent two days surveying Whitmoor Common and one day surveying Chobham Common. We also trained fifteen volunteers. The results from Whitmoor Common were very exciting, with a record number of individuals found. Only one adult was found on Chobham Common and some recommendations for future habitat work to improve the site were identified.