The White-letter Hairstreak, Satyrium w-album, gets its name from the pattern of white scales on the underside of the hindwings forming the letter ‘W’.
Most of the adult life of this butterfly is spent flying around the upper branches of flowering elm trees where their young larvae feed on flower buds and the adults take honeydew, although they will occasionally fly down from the treetops to feed on nectar from brambles, thistles and other flowers. The White-letter Hairstreak is said not to stray far from a given location and will re-use those trees every year – and may even form small colonies centred around a particular tree.
As elm tree species are the sole foodplant for the young stages, the Dutch elm disease did cause concern for the survival of this species, and although the population has declined significantly, fifty years of research and breeding of disease-resistant elms will, hopefully, enable some colonies to thrive.
