Regional Species


White-letter Hairstreak
Satyrium w-album

Photograph by Alan Wagstaff

Regional Species

In North Wales this is a scarce species, known from only a few sites in Flintshire and Denbighshire (and one in Caerns?). Prior to the onset of Dutch Elm Disease the butterfly would have been much more widespread although there are comparatively few records from this period. However, the butterfly is inconspicuous and consequently was likely to have been under-recorded. (It should be added that it is still likely to be under-recorded and may, eventually, turn out to be reasonably common in northeast Wales).

This is a single-brooded species with the adults on the wing throughout July and the first half of August. The butterflies spend most of their time high in the canopies of elm trees (or neighbouring trees of other species such as ash) although occasionally they can be observed nectaring on flowers at ground level. Two species of elm are found in North Wales, Wych Elm (Ulmus glabra) is the commoner but English Elm (Ulmus procera) occurs in lowland areas. Both species can be used as the larval foodplant but whether or not there is any preference is unclear. Eggs are laid on the twigs but do not hatch until the following spring when the trees are coming into flower.

The White-letter Hairstreak is a difficult butterfly to identify but any small dull-looking butterflies seen near elm trees might be this species and would be worth a closer look. As with the Purple Hairstreak, the best way to get a view is usually with a pair of binoculars.