Belfast Telegraph

Why there’s no need to be bugged by explosion of very hungry caterpillars in Northern Ireland

The caterpillars of ermine moths
The caterpillars of ermine moths
Andrew Crory
John Joe Halpin and his hedge webbed by the caterpillars of ermine moths

By Christopher Leebody

Dramatic webbing seen in hedgerows across Northern Ireland is "nothing to worry about", a moth expert has said. 

Andrew Crory spoke out following reports from Kilkeel, Co Down, that mysterious tiny black caterpillars, known as orchard ermine, had devoured entire bushes of foliage.  

The insect typically covers shrubs and hedges in a wispy web, designed to protect larvae from predators. 

Mr Crory is the Northern Ireland moth recorder at Ulster Wildlife and is at the front line when it comes to sightings of butterflies and moths.  

While the 41-year-old admitted that the sight of hundreds of thousands of insects can appear "apocalyptic" to some, the reality is that large numbers of the caterpillar are a normal part of the summer months. 

"They don't destroy," he said. "They defoliate the plants and eat all the leaves, but once done they don't hang around. They never kill the plant.

"Blackthorn and hawthorne are the primary thing they eat.

"The ones that get reported to me are usually at hedgerows by the side of the road. 

"Tens of thousands, if not hundreds of thousands, of caterpillars look dramatic.

"There's nothing to worry about whatsoever.

"Once the webs disappear, you are left with a skeletonised hedge." 

Far from a new phenomenon, Andrew said this was a normal occurrence.

He added people had only started to notice because of methods of planting hedgerows developed over the last few centuries.

"This has been happening all the time - it has been happening every year," Mr Crory said.

"I come across blackthorn bushes at this time of year and they are covered in them.

"People think, 'I've never seen this before, so it must be an invasive species'.

"But they just haven't been looking close enough.

"We only started hedging 400 years ago. We have created a natural habitat for them. We have got to let it run its course.

"You shouldn't get it in the same place every time."

His advice to members of the public who notice the distinctive webbing which covers plants and trees is not to remove or destroy it, but rather to record it on CEDaR, the recording tool used by the Ulster Museum. 

Andrew stressed the data was key for conservation efforts.

"The general pattern for moths is one of decline," he said. "Orchard ermine is a species more prone to boom and bust."

Co Meath man John Joe Halpin (82) recently told how his garden had become overrun by "millions" of tiny black caterpillars.

He said passing motorists stopped to stare at his hedge, thinking he had scorched it with some type of spray.

However, on closer inspection they discovered it was covered in a spider web-like "mist".

"There were millions of them. The bushes were covered until all the leaves were eaten within two to three weeks, then they just disappeared," he said.

The Butterfly Conservation charity echoed the call for the public to be understanding of the insects. 

The organisation's Katie Callaghan said: "Some people may view the caterpillars as a temporary nuisance because they can defoliate some garden shrubs.

"But the shrubs will recover and grow new leaves, so people don't need to worry about their hedges being destroyed.  

"If anything, the amazing webs created by these caterpillars should be seen as a wonder of nature." 

She added: "You normally see the caterpillars and their webs between May and June, but they may have come out a bit later this year.

"It's best to leave them undisturbed.

"The caterpillars are only around for a few weeks before they pupate and disappear. 

"Many people don't realise that moths play a key role in the food chain.

"(They are) also pollinators and indicators of a healthy environment - they really are misunderstood". 

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