Updated: Sep 2, 2022
Did you know, one of the UK's most elusive butterflies lives in the historic Wychwood area? At rest and from a distance little more than smallish triangles, a closer look at the black hairstreak reveals their gorgeous red scalloped edges, black spots, white linear patterning and delicate tail. Though similar to the white-letter hairstreak, the two butterflies can be distinguished with care. White-letter hairstreaks lack the row of black spots on the hind underwing, and the white stripe on their wings forms a distinctive 'W' shape.
Possibly a naturalised introduction, black hairstreaks can only be found in thickets of blackthorn on the heavy clay soils between Oxfordshire and Peterborough. Their caterpillars feed almost exclusively on blackthorn, and initially after metamorphosis the butterflies don't stray far from this shrub. As they age, black hairstreaks move up into the tree canopy where they feed on aphid honeydew. They are seldom seen at ground level, but occasionally descend to feed on the nectar of wild privet and other flowers. Black hairstreaks always settle with their wings closed, a helpful tip for identification.
In recent years, black hairstreaks' status as 'woodland butterflies' has been challenged. Blackthorn is early successional stage scrub, and as woodland matures around it the plant is shaded out. Today black hairstreak colonies are more often found in hedgerows than mature woodland.
Black hairstreaks are usually on the wing in mid-June, but this year are experiencing a late flight period. Keep an eye out for them next you are near a mixed-age blackthorn hedgerow!
Butterfly records are scarce in the historic Wychwood area —something we're working to change in collaboration with Butterfly Conservation's Upper Thames Branch. To find out how you can help, click here.
Photo by Iain Leach.