27 June 2014

Halloween has come early...

Or so it would seem. On your travels out and about, you may have noticed some of our hedgerows covered in strange cobwebs. It appears that rather like our supermarkets bringing out the Easter eggs and Christmas cards 6 months early, that someone or something has been decorating our hedgerows with some spooky webs ready to celebrate all-hallows eve!

Hedges decorated with cobwebs along the Great Langdale Beck 
Caterpillar amongst cobwebs along a hedgerow on the Wray Castle road

But what is encasing trees and hedges in webs and stripping them bare of all their leaves?

The culprit? The ermine moth, this one is the Bird cherry ermine (Yponomeuta evonymella). This is the most common type on the north. The easiest way to identify them is to look at the host plant. (check out ukmoths.org.uk to find out more about moths in the British Isles)

The creature in question is the ermine moth. From my research and speaking to other much more knowledgeable rangers, it seems that this is a fairly natural phenomenon. The ermine moth caterpillars live on host plants (the specific plant depends on which type of ermine moth it is), working together to cover the plant in cobwebs to protect them from parasitic wasps and birds for anything up to 6 weeks, feeding off the leaves underneath. When their delicacy runs out, the caterpillars simply move onto another host plant, devouring the leaves until they are ready to ‘hatch’ into the beautiful ermine moth. Yet despite this destruction, the tree or shrub will recover growing new leaves in that season! The ermine moths will lay their eggs in the host plant a few weeks after pupating, where the caterpillars will over-winter ready to eat the new growth in the spring. So despite the webs looking rather destructive and sometimes sinister, it is not in the interests of the ermine moth to kill of its host plant.

The ermine moth is certainly hungry this year!

The moth usually is small, whitish and long with rows of black dots on its wings depending on the variety. As you can see, it is one of the prettier moths we have in the British Isles. The moths form an important part of the ecosystem, being an excellent food source for many predators and act as excellent pollinators too. Most moths are harmless and even beneficial. Some, like this particular moth, look rather more like a pest. A quick google search brought up lots of examples of cars, bikes and whole rows of parkland trees that have been decimated by the ermine moth larvae or even something else entirely!

It seems sometimes, the ermine moth is not picky about where it chooses to live! (Check out this blog for other freaky places that the ermine moth has chosen to live: https://simonleather.wordpress.com/tag/ermine-moth/)

The ermine moth is usually active in July and August so there is still plenty of time to get out and look in our hedgerows for this almost freaky act of nature. Some of the best examples of devoured hedgerows in the South Lakes I have found tend to be along road edges such as up and over Hawkshead Hill but also river courses such as along Great Langdale Beck towards Elterwater and along some of our footpaths such as the ones around Blelham Tarn. Hedgerows that were planted by the National Trust rangers and volunteers 10+ years ago are acting as host plants to the ermine moth caterpillar. It is a great feeling to see the benefits to wildlife from our conservation work.

It is hard to believe that the hedgerow plants will recover!

It isn’t hard to see why this moth is sometimes considered a pest. Some say it is more prolific this year, which could be due to our warming climate or just an unseasonable warm and sunny spring. Keep an eye out to see what happens in the years to come…. Maybe we won’t notice them so much next year!


  1. It's interesting to read this. I live in Dorset and when the page came up I was hoping the webs were made by spiders. There are lots of tents with bundles of small spiders in in our rough grass at present and I don't know what they are. They seem to have hatched out of a white, papery case instead of the fluffy nests I usually associate with spiders. Do you have these in your grass as well as ermine moths in your hedges? (I'll look out for these now too - unless we are too far south for them.) (My blog is Loose and Leafy - http://looseandleafy.blogspot.co.uk/ )

  2. Hello Lucy

    I haven't noticed any of those spiders in grassland over here but I shall keep an eye out for them. Perhaps the seasonal conditions in Dorset are more appropriate to the spiders?

    As for the ermine moth, you are not too far south to see them. A quick google search will produce images of them on continental Europe too!

    Good luck finding some!


  3. Hello. I've found out what the spiders were who had created the gossamer tents in the grass where I live. They are called 'Nursery Web Spiders'.