Thecla betulae | Brown Hairstreak | Stiallach donn
Ireland: Least Concern (Regan et al., 2010)
Europe: Least Concern (van Swaay et al., 2010)
Climate risk category: High Climate Change Risk; present distribution in Europe can be explained by climate (Settele et al., 2008)
The Brown Hairstreak is not afforded legal protection in Ireland.
Key identification features include:
- Medium size, wingspan: 36 - 45 mm
- Prominent deep-orange band traversing underside of wings
- Distinct orange 'tail' on hind wing
Specialist, found on rich-soil scrub and tall-herb forest clearings. Found only in the Burren and similar limestone pavements areas in Clare, Galway and around Lough Derg, Tipperary. Populations occur in warm south-facing, sheltered clearings where Sloe (Prunus spinosa) occurs with a wide range of height, adjacent to mature woodland. Many Irish sites occur on the margins of turloughs where low stunted Sloe bushes occur just above the winter shoreline. Males roost on leaves of trees high in the canopy, occasionally descending; large Ash (Fraxinus excelsior) trees are particularly favoured for assembling, and are referred to as “master trees”. The females tend to roost closer to the ground, often on Bramble (Rubus fruticosus agg.) flowers or foliage, and are therefore more often observed. In weak light the wings are held open, but in strong sunlight they tend to be closed (Bond & Gittings, 2008).
Univoltine: from July to September with peak abundances being observed in late August.
Eggs are laid on the upperside of a fork in the small branches or twigs of the foodplant, usually placed singly. Most eggs are found at a height of 0.2-1 m, but others can be found up to 2.5 m. The larva feeds initially on an opening bud of the foodplant, but later on the leaves. It feeds by night, returning to a silken pad spun on the leaf underside by day. Pupation occurs about June, in leaf detritus and this species overwinters as an egg (Bond & Gittings, 2008).
Specialist, the larvae feed exclusively on Blackthorn/Sloe (Prunus spinosa).
Generalist, adults commonly feed on honeydew/sap but nectar sources include: Bramble (Rubus fruticosus), Devil's-bit Scabious (Succisa pratensis), Hemp Agrimony (Eupatorium cannabinum), Hogweed / Angelica (Umbelliferae), Ragwort (Senecio jacobaea) and Thistles (Cirsium spp. and Carduus spp.) are also used.
Records submitted to Data Centre in 2021
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Bond, K.G.M. and Gittings, T. 2008. Database of Irish Lepidoptera. 1 - Macrohabitats, microsites and traits of Noctuidae and butterflies. Irish Wildlife Manuals, No. 35. National Parks and Wildlife Service, Department of the Environment, Heritage and Local Government, Dublin, Ireland.
Regan, E.C., Nelson, B., Aldwell, B., Bertrand, C., Bond, K., Harding, J., Nash, D., Nixon, D. and Wilson, C.J. 2010. Ireland Red List No. 4 – Butterflies. National Parks and Wildlife Service, Department of the Environment, Heritage and Local Government, Ireland.
Settele, J., Kudrna, O., Harpke, A., Kühn, I., Van Swaay, C., Verovnik, R., Warren, M.S., Wiemers, M., Hanspach, J., Hickler, T. and Kühn, E. 2008. Climatic risk atlas of European butterflies. Sofia-Moscow: Pensoft.
Van Swaay, C., Cuttelod, A., Collins, S., Maes, D., López Munguira, M., Šašic, M., Settele, J., Verovnik, R., Verstrael, T., Warren, M., Wiemers, M. and Wynhof, I. 2010. European Red List of Butterflies. Luxembourg: Publications Office of the European Union.