Northern Brown Argus
Northern Brown Argus (Aricia artaxerxes) was discovered on Arthur’s Seat in Edinburgh in 1795, and there was much debate as to whether they were a distinct species or just a subspecies of the Brown Argus (Aricia agestis). This has now been settled unequivocally, and it is a full species that also occurs in mountains in Europe, where it is known as the Mountain Argus. The white-spotted form though, appears to be unique to Britain.
The populations of northern England usually lack the white forewing spots, and also have black-spotted undersides, making them look more like Brown Argus. In this respect they also resemble the European forms of Mountain Argus. It does not seem to be particularly well-known (it isn’t mentioned in either Jeremy Thomas’ excellent book, or the Millennium Atlas) but the full white-spotted form occurs in coastal populations in County Durham (as well as Scotland) making up about 20% in some populations. The inland colonies in County Durham, though just a few miles away rarely, if ever produce the full white-spotted form.
This photograph was taken in one tiny colony on the County Durham coast. They are single brooded, flying from late June, and their caterpillars feed on Rock Rose (Helianthemum nummularium). The habitat is extremely steep crumbling cliffs, where the necessary open areas seem to be maintained by landslips rather than grazing.
Northern Brown Argus
Northern Brown Argus (Aricia artaxerxes) was discovered on Arthur’s Seat in Edinburgh in 1795, and there was much debate as to whether they were a distinct species or just a subspecies of the Brown Argus (Aricia agestis). This has now been settled unequivocally, and it is a full species that also occurs in mountains in Europe, where it is known as the Mountain Argus. The white-spotted form though, appears to be unique to Britain.
The populations of northern England usually lack the white forewing spots, and also have black-spotted undersides, making them look more like Brown Argus. In this respect they also resemble the European forms of Mountain Argus. It does not seem to be particularly well-known (it isn’t mentioned in either Jeremy Thomas’ excellent book, or the Millennium Atlas) but the full white-spotted form occurs in coastal populations in County Durham (as well as Scotland) making up about 20% in some populations. The inland colonies in County Durham, though just a few miles away rarely, if ever produce the full white-spotted form.
This photograph was taken in one tiny colony on the County Durham coast. They are single brooded, flying from late June, and their caterpillars feed on Rock Rose (Helianthemum nummularium). The habitat is extremely steep crumbling cliffs, where the necessary open areas seem to be maintained by landslips rather than grazing.