A Bit of a Panic

Dear Readers, when I was wandering through Cherry Tree Wood here in East Finchley a few weeks ago, I was fascinated to see that some of the trees had these ghostly nets in them. The silk is similar to that of spiders, but because it is protective rather than used to catch insects, it’s opaque and surprisingly strong. In the midst of the tent above I could see frass, the black droppings of caterpillars. Some little critters had obviously been having a lovely time eating the new leaves. It didn’t take me long to find the culprits – the caterpillars of the bird-cherry ermine moth (Yponomeuta yvonemella).

Bird cherry with webs of the Bird Cherry Ermine moth (Yponomeuta yvonemella)

These caterpillars will be gone by the end of June, giving the tree plenty of time to recover. After all, compared with some webs,  this was a mild one.

Photo One from http://www.growsonyou.com/photo/slideshow/157704-bird-cherry-tree-ermine-moths-larvae/all

A dramatic bird cherry ermine moth web in Essex (Photo One)

There is definitely safety in numbers – when the caterpillars all emerge at the same time it makes it less likely that an individual larva will be eaten. Furthermore, even the most diligent blue tit won’t want to foul her feathers with too much of that sticky stuff.

The caterpillars will pupate briefly, and then this rather elegant moth emerges. You can see how its resemblance to a winter-coated stoat gave it its name – just think of the white, black-spotted fur that lines the ceremonial robes of mayors and royalty. I always think that every black spot was once the tip of the tail of a small predator, and count how many died to make each outfit, but maybe that’s just me.

Photo Two by By David Short from Windsor, UK - Bird cherry ermine (rp), CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=63856375

Bird cherry ermine moth (Photo Two)

There are several other species of ermine moth in the UK, the commonest being the orchard ermine (which feeds mainly on hawthorn and blackthorn) and the spindle ermine that munches through (predictably) spindle. None of them are any threat to the plant, and their populations will naturally fluctuate according to the weather and to the availability of food and the number of predators.

As I was perusing the ermines and getting a few photographs, I was accosted by some young women who were anxious for their children.

‘Are these those dangerous caterpillars that I heard about on the news?’ they asked.

I was able to reassure them. The ‘dangerous caterpillars’ are the young of the oak processionary moth, a European mainland native that has been imported (just like ash dieback) on young trees for landscaping. These insects have been spotted in several places in West London, and they are considered a problem because they are ‘urticareous’ – that is, their hairs are likely to cause dermatitis and even asthma if inhaled. The clue to their behaviour is in the name: the processionary moth caterpillars follow one another around en masse. Their nests tend to be on the branches and trunks of oak trees, never among the leaves as with the ermine moths. You need to be in close contact with the caterpillars for them to cause any harm. The Forestry Commission are treating the outbreaks that they know about (probably with huge doses of biocides) and if you spot any actual Oak Processionary Moth caterpillars you can report it here.

Photo Three by By Kleuske - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19940595

Oak Processionary moth caterpillars having a trot around a tree trunk (Photo Three)

I do wonder, however, how many perfectly harmless caterpillars have been killed as a result of all the quasi-hysterical news reporting of the oak processionary moth. The story has all the ingredients for a media storm: invaders from overseas: a danger to children: an attack on that very bastion of Englishness, the oak tree. Many people have a fear of insects, and most of us have a fear of insects in very large numbers. I suspect that some people might have seen a caterpillar net in their garden and doused it with insecticide without stopping to identify it. Which would be a real shame, because some extremely rare species superficially resemble the oak processionary moth.

One of the most endangered is the Small Eggar (Eriogaster lanestris). This species lives in hawthorn, blackthorn and birch, and the caterpillars create a nest about the size of a small football. The larvae are attuned to one another and it’s believed that they communicate about where the best feeding opportunities are, before leaving to forage en masse. They have been under extreme pressure due to the loss of habitat in the countryside, and so are more likely to come into contact with humans. What a shame it would be to lose this creature because of mistaken identity.

Photo Four by By User:MarkusHagenlocher - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2151016

Small Eggar caterpillar (Photo Four)

Photo Five by By Hans Gasperl [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons

Small Eggar silk tent (Photo Five)

Photo Six by [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons

Adult Small Eggar (Photo Six)

Another possible victim of over-enthusiastic caterpillar killing is the Nationally Scarce lackey moth (Malacosoma neustris), which has some of the most appealing larvae of all lepidoptera, at least to me – I spent a lot of time playing with these creatures as a child, and although they too could set off dermatitis in those who are susceptible, I never had any ill effects. These caterpillars also live in nets and their preferred foodplants include oak. cherry. plum, apple, willow and hornbeam. You can see how these chaps, spotted in an oak tree, could be doomed from the start, although their caterpillars look very different from those of the oak processionary moth, and their behaviour is quite different.

Photo Seven by By H. Krisp - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=19806408

Lackey moth caterpillar (Photo Seven)

The eggs of the lackey moth look as if they’re made of ivory, and are always laid around a twig. I wonder if the mother gets dizzy laying them?

Photo Eight by By José Manuel Benito Álvarez [CC BY-SA 2.5 es (https://creativecommons.org/licenses/by-sa/2.5/es/deed.en)], via Wikimedia Commons

Lackey Moth eggs (Photo Eight)

In fact, to our human eyes, the adult moth is the least beautiful stage of the lackey moth’s life, although it is still a very handsome creature.

Photo Nine by By Ben Sale from UK ([1634] The Lackey (Malacosoma neustria)) [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Lackey moth adult (Photo Nine)

So it seems to me that the ability to identify an oak tree, and to tell the difference between a lackey moth caterpillar with its cartoon-like blue face and the ultra-furry oak processionary moth caterpillar are what’s required to prevent the accidental extermination of rare moths who are already under extreme pressure. And also, it helps if, having learned these things, we communicate them to our children. No one wants their little ones to be bitten or stung or hurt in any way, but the best way of keeping them safe is to help them to understand what’s safe and what’s not. Children are naturally curious, and when they’re outdoors they will probably fall off of logs, get stung by wasps and come home covered in bruises and dirty. It’s hard, I know, but we cannot protect those that we love from things that hurt them and nor should we. How can we learn resilience without a little adversity? And besides, exploring the outside world and discovering things for ourselves is so much fun that it will bring us joy for a lifetime.

Photo Credits

Photo One from http://www.growsonyou.com/photo/slideshow/157704-bird-cherry-tree-ermine-moths-larvae/all

Photo Two by By David Short from Windsor, UK – Bird cherry ermine (rp), CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=63856375

Photo Three by By Kleuske – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19940595

Photo Four by By User:MarkusHagenlocher – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2151016

Photo Five by By Hans Gasperl [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons

Photo Six by [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons

Photo Seven by By H. Krisp – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=19806408

Photo Eight by By José Manuel Benito Álvarez [CC BY-SA 2.5 es (https://creativecommons.org/licenses/by-sa/2.5/es/deed.en)], via Wikimedia Commons

Photo Nine by By Ben Sale from UK ([1634] The Lackey (Malacosoma neustria)) [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

 

 

14 thoughts on “A Bit of a Panic

    1. Bug Woman Post author

      The nests are usually high up in the trees so I guess people don’t get to see them unless they’re into tree-climbing. Fortunately these were low enough to get a good look……

      Reply
    1. Bug Woman Post author

      Agreed, and scientists would agree with you too….there’s an increasing body of evidence that our obsession with antimicrobial wipes and sprays is damaging our immunity.

      Reply
  1. Fran and Bobby Freelove

    You are quite right about the hysteria caused by the media, it usually moves from one thing to another, caterpillars, foxes, squirrels, the list is endless. When we worked in horticulture we always had people asking our advice on how to kill eveything in sight, even down to earthworms and woodlice. It’s really sad, but easy to prevent if people are put right and given the right advice and explained to why these creatures are beneficial. We choose not to use insecticides and herbicides and our gardens are heaving with beautiful healthy plants and wildlife. It’s all about getting the balance right, we believe everything is here for a reason.

    Reply
    1. Bug Woman Post author

      Agreed, Fran and Bobby. Usually, people just don’t know about the animals and plants that they kill, they just want them gone, without realising that they’re part of a web. I well remember all the hedgehogs that used to pass through the garden when I was growing up, and now they’re all gone, a victim of habitat change and slug pellets.

      Reply
  2. tonytomeo

    When there were still orchards in the Santa Clara Valley, such tents were occasionally seen in the oak trees near the creeks on the edges of the orchards. They only seemed to live near the orchards. They did not appear in oaks that were not adjacent to orchards.

    Reply
      1. tonytomeo

        Back then, I remember being told that they liked the apricot trees, but did not start out there. That makes no sense because the caterpillars could not fly, so it would have been a long walk to the apricot trees. I think that they lived their lives in the oak trees. Similar caterpillars that made tents in apple and pear trees were uncommon because the trees were pruned every winter.

  3. Toffeeapple

    If only children were given this information and encouraged to make observations I feel sure that things would change.

    Reply
  4. Pingback: The Long Hot Summer | Bug Woman – Adventures in London

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