Regional Species


Large Heath
Coenonympha tullia

Photograph by Janet Graham (Cors Goch, Trawsfynydd)

Regional Species

The Large Heath is a habitat specialist which can only be found in a few localities in North Wales. The species' requirement is for extensive areas of bog with Hare’s-tail Cotton-grass (Eriophorum vaginatum), the larval foodplant and sources of nectar such as Cross-leaved Heath (Erica tetralix). Although both these plants occur widely throughout the hills of North Wales, and indeed the Eriophorum is an all too common indicator of heavy grazing, the butterflies are only found on large, more-or-less level areas of wet ground. One way to find such places is to look at the OS maps and pick out areas where the contours are widely spaced; these are the sites that are worth inspecting. Butterflies have been seen as high as 460m but may well occur higher than that.

Additional colonies have been discovered in recent years and old sites have been reconfirmed after long gaps with no records. However, there are still large areas that have not been explored recently and it is very likely that there are further colonies to be discovered. All records for this species are valuable and should be passed on to the appropriate County Recorder.

Threats to the species include sheep grazing and heather burning - it is thought that two colonies may have been lost in the disastrous fires on the Migneint in spring 2003.

This is usually considered to be a sedentary species, an appropriate adaptation to life on an isolated patch of habitat. However, in North Wales, there are recent records of individuals having been seen, in unsuitable habitat, some miles from the nearest known colony so it is possible that these upland populations may experience some degree of genetic interchange.

Several races are recognised in Britain of which two occur in North Wales. Race polydama is the wide-ranging upland form whilst the more heavily spotted form known as davus is found on Fenn’s Moss.

The butterfly flies from about mid-June to the end of July. Ova are laid on the Eriophorum and the resulting larvae overwinter in their second or third instar.

Confusion is possible with the similar looking Small Heath, which is often found flying alongside its larger relative. With experience the Large Heath can be distinguished by its darker appearance and characteristic manner of flying. To be certain which species is involved an examination of the underwing pattern will reveal the more numerous ocelli on the Large Heath.