Belfast Telegraph

Experts in a flap as rare holly blue butterfly is spotted in a Co Down wood... thanks to our mild weather

By Linda Stewart

The once rare holly blue butterfly has been discovered in a recently planted woodland in Co Down, marking a major success story for the species.

The insect was once rare in Ireland, found only in eastern areas, but has undergone a remarkable revival in the past decade, taking advantage of a series of favourable spring and autumn seasons.

Holly blue butterflies depend on both holly and ivy as food plants, hatching caterpillars on young holly buds and eating the tender leaves in spring. In autumn, a second flush of caterpillars hatches at a time when holly leaves are too tough to eat and these feed off the ivy plant, according to Butterfly Conservation spokeswoman Catherine Bertrand.

The first holly blue was found recently at Glasswater Wood in Crossgar by Butterfly Conservation branch secretary David Nixon, who spotted it flying around the wood's sole holly tree.

More holly blues made an appearance at a special May bank holiday event at the woodland where visitors planted 30 holly trees to encourage the species.

"It used to be very, very limited in distribution in Ireland and was only found in the east of the country." Catherine said.

"Reserves were declared simply because it was present, such as the Bohill Wood reserve in Co Down.

"It's now been recorded in all six counties in Northern Ireland. It's a real success story.

"Anyone who has holly trees in their garden may get to see it now – just watch out for very pretty, small bright blue butterflies flying up around the tree, looking for a place to lay their eggs. It could be in anybody's garden."

The holly blue was once a rare sight throughout Ireland, but has been expanding its range in recent years.

Rosie Irwin of the Woodland Trust said: "We were absolutely delighted to find that Glasswater Wood is home to the holly blue.

"These butterflies thrive in sunny, sheltered sites and are an indicator that the habitat is good for a range of other species.

"The holly blue's caterpillars feed on a number of plants – including holly, bramble and ivy."

In 2000 the wood was planted with a mixture of native trees – mostly oak, ash, willow and alder. Habitats include mature hedgerows and a corridor of blackthorn.

Anyone who spots a holly blue is urged to submit their sighting to the Butterfly Conservation webpage at or the Facebook page.


The holly blue emerges well before the other blue butterflies in spring. It flies high around bushes and trees, unlike other grassland blues which tend to stay near ground level. Look out for its sky-blue upper-wings and powder-blue under-wings with black spots.

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