Butterflies of the World - Lifecycle, Ecology, Taxonomy, Conservation, Photography, Butterfly Holidays, Photo Galleries, Book Reviews and more.........
Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.
Butterflies of Britain & Europe
 
Brown Hairstreak
Thecla betulae LINNAEUS, 1758
Family - LYCAENIDAE
subfamily - THECLINAE
Tribe - EUMAEINI
 
 introduction | habitats | lifecycle | adult behaviour
 
Brown Hairstreak Thecla betulae, female, Hampshire, England
 
Introduction
 
The Brown Hairstreak is the last of the single-brooded butterflies to emerge in Britain, the males usually appearing around 4th August, and the females a week later.
 
It gets it's common name from the white hair-line streaks on the underside hindwings. The scientific name betulae is a misnomer - the word translates as "birch", but the butterfly is not in any way associated with birch trees.
 
The butterfly is widely distributed across most of Europe, but absent from Portugal, southern Spain, Italy, the Mediterranean islands, Scotland and northern Scandinavia. Beyond Europe it occurs eastward across temperate Asia to Korea.
 
There are no other similar species in Europe, but novices often confuse this butterfly with the male Vapourer moth Orgyia antiqua which also flies around the tops of trees on sunny days. The Vapourer has a wild and erratic twisting flight over long distances, whereas the Brown Hairstreak tends to undertake very short flights, usually settling high in ash trees, but occasionally descending to visit flowers.
 
Brown Hairstreak Thecla betulae, male, Hampshire, England
 
Habitats
 
In Britain this beautiful butterfly is a rarity, occurring in small discrete colonies scattered mainly across Hampshire, West Sussex, Dorset, Devon, Somerset, Oxfordshire and the western counties of Wales and Ireland.
 
This species breeds mainly along unmanaged blackthorn hedgerows, often in association with ash trees which the adults use as assembly points when seeking mates. There are also colonies on sheltered scrubby downland, along woodland edges, and at the edges of rides in mixed or deciduous forests. The butterfly can sometimes turn up in very odd situations, e.g. I once found an immaculate freshly emerged female in the middle of a beech plantation in West Sussex, half a kilometre away from the nearest blackthorn bush ( larval foodplant ), and 3 kilometres from the nearest known breeding site.
 
Brown Hairstreak Thecla betulae, female, ovipositing on blackthorn
 
Lifecycle
 
The best way to locate colonies of this species is to search for the dome-shaped white eggs, which are laid singly or in pairs in the forks of blackthorn twigs, and are very easy to find in winter when the blackthorns Prunus spinosa are devoid of leaves.
 
ovum in fork of blackthorn
 
It is worth searching almost any blackthorn bush, although the females prefer to lay on young growth. I have found eggs on small isolated bushes growing along a track in a spruce plantation, and on large bushes on north-facing grassland slopes on the South Downs, but blackthorn hedgerows or mosaics of grassland / blackthorn thicket are better bets, particularly if there are ash trees nearby.
 
The eggs are laid in August, but do not hatch until the following April or May, coinciding with the appearance of the blackthorn buds.
 
The plump larvae are green with rows of short diagonal whitish dashes along the sides, and very slightly hairy. They live solitarily, feed nocturnally, and rest during the day on the underside of blackthorn leaves.
 
When fully grown they descend to pupate amongst leaf litter and broken twigs beneath the blackthorn bushes. Some authors state that the pupa can also be found attached to the upper surface of leaves or twigs on the bushes. The pupa is dark brown and shiny, with darker freckling on the abdomen. It is reportedly attended by ants Lasius niger.
 
Brown Hairstreak Thecla betulae, male on hemp agrimony, Hampshire, England
 
Adult behaviour

 

Brown Hairstreaks begin to emerge in the first week of August. Freshly emerged males can sometimes be seen resting on the terminal leaves of ash saplings, but normally fly straight to the top of the tallest ash tree in the vicinity, where courtship and copulation takes place. In the absence of ash trees sycamore or birch are sometimes used.

 

After copulation the males generally remain high in the ash trees, where they feed on the aphid secretions which coat the upper surface of oak and ash leaves, high in the tree tops. They will occasionally descend to nectar at hemp agrimony or other flowers.

 

Females spend most of their lives at lower levels, resting or walking about over young blackthorn twigs, constantly probing with their abdomens to locate suitable places to lay their eggs. Between bouts of egg-laying they often sit for long periods on blackthorn bushes or ash saplings. They periodically visit nectar sources including hemp agrimony, bramble blossom, ragwort, fleabane and various umbellifers, although their choice of nectar source tends to vary from site to site. I have also seen them imbibing honey-dew from hazel leaves.

 

Brown Hairstreak Thecla betulae, female basking between bouts of egg-laying, Hampshire
 

Normally both sexes rest and feed with their wings tightly closed, but in weak hazy sunlight the females can sometimes be found basking on blackthorn bushes, or on low foliage.

 
                                                       
Almost every British and European species of butterfly is declining rapidly in numbers, due in most cases to loss or degradation of habitats.
 
You can help to reverse the decline by supporting conservation organisations which purchase and manage habitats as nature reserves, and which lobby government at local, national and international levels, often very successfully, to bring about changes in farming, forestry and urban development policies.
 
Please contact the conservation organisations for advice on how you can help protect British and European butterflies and their habitats. You may be able to offer practical help e.g. by monitoring butterfly populations or helping to manage nature reserves. Donations to these organisations enable them to employ ecologists and biologists. Even if you are unable to provide such help, merely having your name on the membership list can be a powerful tool for conservation organisations wishing to demonstrate the levels of support they have for their policies.

 

 
Text and photographs protected by Copyright © Adrian Hoskins 2007-2008, and must not be reproduced or published in part or in whole elsewhere in any form without written permission from Adrian Hoskins. Breach of copyright will be pursued by litigation.
 
Website designed, produced and owned by Adrian Hoskins