Leptidea juvernica Williams, 1946
Family: Pieridae

A small white butterfly, often described as dainty. The wings appear slightly elongated and more rounded than other ‘white’ butterflies. Although its name implies that it is a woodland species it is found mainly in open areas with patches of scrub. It is more common in Counties Armagh, Down and Fermanagh and considered local in Antrim, Londonderry and Tyrone. This butterfly is found nowhere else in the UK.

In brief

• Resident in Northern Ireland

• Found in open scrubby grassland habitats

• Peak adult sightings May and June

• This species has declined and Northern Ireland holds 100 per cent of the UK population

• Reason for decline: Not well known but most likely loss of habitat.

Species description
This is the most delicate of our ‘white’ butterflies. Adults have elongated, rounded white wings with grey wing tips. They only settle with their wings closed showing clearly the patchy grey and white patterning of the underside of the wings and the greenish tinge of the underside of the hindwing. Their slow fluttering flight is quite distinctive and they never bask in the sun.

Life cycle
Adults have been recorded from early April to late September but the main flight period is May and June. The later sightings in August and September indicate an occasional second brood. Eggs are laid singly on the upper parts of the larval foodplants (yellow vetchling and bird’s-foot trefoil) and hatch after about ten days. The well-camouflaged caterpillar tends to eat the more nutritious growth at the top of the foodplant and, after about four weeks, moves off to pupate in tall grasses or scrub where it spends the winter in hibernation.

Similar species
Two species of ‘wood white’ butterfly occur in Ireland and they both look identical in the field. The only way to tell them apart with certainty is by examination of the internal organs. It has been discovered that the wood white Leptidea sinapis occurs only in Counties Clare and Galway and the cryptic wood white Leptidea juvernica is the only confirmed species in Northern Ireland. The vast majority of Northern Ireland records are unconfirmed but are therefore presumed to be cryptic wood white.

How to see this species
Réal’s wood white is best seen on a sunny day in May or June. The preferred habitat is open flower-rich grassland, abandoned quarries, hedges, verges and limestone grassland, all usually with patches of scrub. This butterfly is more common in the lowland areas of Counties Fermanagh, Armagh and Down although it is recorded from all counties. Relevant access permissions should always be sought prior to visiting any sites.

Current status
The records indicate that this butterfly was formerly exceptionally rare in Northern Ireland and started spreading northwards in the 1950s and 1960s but now appears to be in retreat.

Why is this species a priority in Northern Ireland?

• It has declined and Northern Ireland holds 100 per cent of the UK population.

Threats/Causes of decline
Loss of habitat and changes in land use could have a major bearing on the future of this delicate little butterfly.

Conservation of this species

Current action

• Cryptic wood white is found on a number of sites which have been designated as ASSIs. It also occurs on a number of National Nature Reserves

• Research into the species and its relationship with wood white has been undertaken by Northern Irish experts.

Proposed objectives/actions

• Maintain the number of viable populations of the species.

What you can do

• Report all butterfly sightings, especially cryptic wood white butterflies or caterpillars, to Butterfly Conservation Northern Ireland or use the BCNI sightings web page at http://www.bcni.org.uk/submitsighting.php. The BCNI database is managed by CEDaR and these records will then be used to update the Butterflies and Moths of Northern Ireland website.
• Join Butterfly Conservation. Butterflies and Moths are in serious decline — with your support Butterfly Conservation can take action to reverse this.

Further information

Links
Butterflies and Moths of Northern Ireland.

A UK page with some information

Further information on ASSIs and NNRs

Literature
Asher, J., Warren, M., Fox, R., Harding, P., Jeffcoate, G. and Jeffcoate, S. (2001). The Millennium Atlas of Butterflies in Britain and Ireland. Oxford.

Lewington, R. (2003). Pocket Guide to the Butterflies of Great Britain and Ireland. BWP.

Tomlinson, D. and Still, R. (2002). Britain’s Butterflies. Wild Guides.

Text written by:
Allen & Mellon Environmental Ltd.

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