Regional Species


Small Pearl-bordered Fritillary
Boloria selene

Photograph by Janet Graham

Regional Species

We are fortunate in North Wales that this is still a relatively common butterfly as in many other parts of Britain the species has already been driven to extinction or survives in only a few protected colonies. However, even in Wales there has undoubtedly been a drastic decline in numbers, a trend that shows little sign of being halted. Sheep are the problem for this butterfly as they find the larval foodplant, Marsh Violet (Viola palustris), highly palatable. Sheep numbers in Wales have roughly quadrupled since the Second World War and in the same period a considerable proportion of the land has been lost to afforestation. Thus the effective stocking density of sheep has risen by even more than the factor of four. Together with the destruction of suitable habitat through land drainage and reseeding, there are now few places left on farmland for this butterfly to survive. Ironically, although conifer plantations have destroyed so much fritillary habitat, it is within their confines that many of our remaining colonies are to be found. Bogs and streamsides that were too wet to plant now provide a refuge for the butterflies. Basically, wherever there are enough Marsh Violets the butterfly is likely to be seen and suitable habitat still occurs from sea level to at least 500m.

As already mentioned the principal larval foodplant is Marsh Violet but Common Dog-violet (Viola riviniana) may also be used. The third common violet species Heath Dog-violet (Viola canina), which can be abundant in sand dunes, appears to be used less frequently as the butterfly is often absent from this habitat. Adults can be seen from late May to the end of July, peaking in about the first week of July. The larvae, which overwinter in their fourth instar, are seldom seen as they hide themselves away by day.

Unfortunately, the Small Pearl-bordered Fritillary is very similar in appearance to its close relative, the Pearl-bordered Fritillary and there has undoubtedly been much confusion between the two species in the past. At the present time, the Small Pearl-bordered is very much more abundant and almost all sightings will be of this species. There are usually small differences in the pattern on the upper wing surface and these are clearly visible in the two photographs used here. In the Small Pearl-bordered Fritillary the outer row of enclosed spots is paler and yellowier and contrasts with the ground colour of the remainder of the wing whereas in the Pearl-bordered the colour is the same. However, this is not considered a reliable way to distinguish the two species and to be completely sure of the identification it is best to net the butterfly and examine the underside pattern carefully.