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About the dark-bordered beauty moth
Dark-bordered beauty moth caterpillar on aspen
Lifestyle
The dark-bordered beauty moth lays eggs that are flattish oval in shape, with a depression at the top. They begin a pale yellow colour and turn red with age. The moth has only one brood per year and survives over winter as an egg. The eggs hatch in May and adults have developed by late July and fly until early August. The egg contains only very small food reserves to last between September and May and these can run short during mild winters. Other moths are careful to hide their eggs away but, for unknown reasons, possibly related to their larval food, the dark-bordered beauty places its eggs fully exposed on the bark of the tree.
Moth larvae feed and grow moulting along the way to remove the old cuticle and replace it with a bigger one. Moulting larvae are the easiest prey, especially to birds, as they are extremely vulnerable while trying to crawl out of their old cuticle. The larvae feed on creeping willow at the English sites and on low regrowth of aspen in Scotland. Once the final larval stage has been reached the next moult will produce the pupal stage.
All moth pupae have a smooth shiny outer surface with the body parts clearly identifiable and the eyes obvious at one end. During the pupal stage internal reorganisation takes place and this can take a few days in some species including the dark-bordered beauty. Other species choose to overwinter at this stage. Emergence of the moth usually occurs in the early morning but can vary between species. It is generally timed to give the adult time to dry and expand their wings before being at risk of predation. When a moth emerges from its pupa the wings are crumpled and soft, but the moth finds a secure foothold and then forces a fluid through the veins which expands them rapidly. Once they are full size this fluid is withdrawn and the wing hardens.
Adult dark-bordered beauty moths do not live for long as this is the stage for mating and egg laying. The adult moth can travel over great distances to find new habitats, many dying before they have been able to find suitable places to lay their eggs.
Concerns
The decline of aspen stands in Scotland has been a major problem for this moth. Large areas of aspen have been lost due to road and building developments and there has been insufficient regeneration or replanting resulting in a major loss of habitat.
Management of aspen stands is needed to extend core areas, link isolated stands, and encourage regrowth through exclusion of livestock and rabbits. This should maintain and eventually increase populations at the known sites in Scotland. Less is known about the English populations; ascertaining their status will be the first job, and then ensuring the sites are managed sympathetically.
Identification
The dark-bordered beauty has a wing span of 26-29mm. Male and female are similar in size with a broad brown border on the outer edge of the wing, the rest of the wing is orange-brown in colour.
The male the vein is patterned in dark brown and a brown spot can be seen central to each quadrant of wing. In the female dark brown veining is localised close to the head and similar brown spots can be seen more clearly.
It is distinguished from the similar bordered beauty moth by having a broader edging that runs parallel to the wing edge rather than tapering away at the wing corners.
The female moth is sluggish and rarely seen. Male moths fly for an hour after sunrise and again from dusk onwards.
Male moths may be attracted by light and are seen between late July and August.
The caterpillar may be seen from May to early July on creeping willow at the English sites or aspen regrowth at the Scottish sites. It is brown with grey on the back of the first four rings and a whitish underside. A dark mark at about the middle of the back has two thin but fairly distinct white lines on either side.
Range and numbers
The dark-bordered beauty has been recorded from most countries in Europe. It is generally associated with northern or upland habitats.
In the UK only four small populations are known: north-east Yorkshire; near Hexham (Northumberland); near Balmoral (Aberdeenshire) and in Strathspey (Moray). Old records suggest that the moth should be present at a site in Roxburghshire but its status here is unclear at present.
Studies
RSPB and Butterfly Conservation are working together to establish a regular monitoring programme at known sites, along with surveys into the status of the moth at other suitable aspen woodlands in Scotland. These surveys will determine what further action needs to be taken.
During 2001, local volunteers and RSPB staff were trained in survey and monitoring techniques. In 2001 and 2002 we co-funded and helped organise surveys of historic sites in North-East Scotland with Butterfly Conservation, to determine the species status. The moth was found at two historic sites in Speyside and Deeside and at a new site in Deeside. The surveys have been combined with a study of habitat requirements. In 2002 surveyors in Scotland concentrated on detailed observations of caterpillar behaviour and flight times of adults.
We have encouraged the sharing of information between the findings in Scotland and work undertaken in England by Butterfly Conservation during 2002. Here, it was recorded at only one of the two known sites and none of the potential sites and it lives in more open habitat and feeds mainly on creeping willow, Salix repens. Even less is known of its ecology in this habitat and more detailed study is required in order to plan habitat management to meet the needs of this moth.
Conservation
The objectives of the UK Biodiversity Action Plan for the dark-bordered beauty moth will be achieved through protection and sympathetic management of existing sites and of any new sites discovered during surveys. Various aspen woodlands in Scotland already have management plans aiming to encourage regeneration through exclusion of livestock, and to extend the existing stands.
It may become necessary to re-establish the dark bordered beauty at suitable sites, one of which could be the RSPB's reserve at Insh Marshes. It is hoped to have 10 viable populations within the historic range by 2010.
Implementation of this action plan will also be beneficial to the hoverfly Hammerschmidtia ferruginea, another BAP priority species living in aspen woodland.
How to help
These moths are generally found in conserved areas, when walking through these areas you should always stay with the marked paths as movement through other areas can disturb insect sites. Although this moth is not protected by law, larvae and adults should not be collected.
The RSPB Voluntary Wardening Scheme is run at the RSPB's Insh Marshes nature reserve. Copies of the Voluntary Wardening Scheme Information Pack are available from theYouth and Volunteers Department, RSPB, The Lodge, Sandy, Bedfordshire, SG19 2DL.
The RSPB is about more than just birds and regards the conservation of a wider biodiverse countryside as a high priority. You can help the Society to achieve these aims by joining or persuading a friend to join. Help with fund-raising is always needed so that research and practical conservation management can take place to help protect wildlife such as this moth.
Last modified: 02 October 2006