Only one subspecies of the scotch argus Erebia aethiops aethiops (Esper) exists in Britain

Abstract

The scotch argus (Erebia aethiops) is a locally abundant butterfly typically on the wing during August in large areas of Scotland and at two sites in northern England. It is currently accepted by many that in Scotland two subspecies – Erebia aethiops caledonia (Vérity) and Erebia aethiops aethiops (Esper) - exist in different areas and that these differ morphologically. E. a. caledonia is slightly smaller and has three ocelli (eyespots) on the upper fore and hind wing, whereas E. a. aethiops has four or more ocelli. We have surveyed four areas presumed to hold either one or the other subspecies but found that both forms exist in all areas and that E. a. caledonia was always the more common form. While there may be other areas that are the sole domain of one or the other form, our findings do not support the contention that two subspecies exist. These findings and the fact that there is continuous variation between the two variant extremes represented by E. a. caledonia and E. a. aethiops leads us to suggest that the subspecies E. a. caledonia is invalid and that this form ought to be considered only as a variant of the nominate species Erebia aethiops aethiops (Esper).