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  • Writer's pictureGraham Tapp

JUNE 2024 - Caterpillars and Moths

Mid-May into June and sometimes into July, you might see ghost bushes and trees in our hedgerows, silky white, some completely opaque, others more open like fishnet stockings. What are these soon-to-be-gone apparitions? What is their purpose? Why are they there?.

You may drive a route to work every week and never see this spectacular feat of nature; you may walk regularly for miles on our local footpaths for years and still never see one.

Even at sixty-nine, I had never witnessed this act of nature until last year when they suddenly appeared in several local places. There were actually three or four between Baldock and Buntingford; one tree in particular was white from top to bottom, a truly mesmerising sight.

It is true that they have been around for years but rarely appeared in the splendid way they do now.

These trees and bushes are actually covered in cobwebs placed there by caterpillars. The silky white covering is spun and laid carefully to provide protection from predators while they feed on the leaves and soft shoots of the bush or tree. The plants, trees, and shrubs they are feeding on can become completely bald in a matter of weeks, and they will become just bare sticks.

Who are the Culprits?

The culprits are a group of small moth caterpillars called Ermine Moths. There are eight, but only the Orchard Ermine, Spindle Ermine, and Bird-cherry Ermine create the large amount of webbing that covers trees and shrubs; in the light of a bright moon, it is easy to imagine you are looking at a ghost.


Are the Caterpillars and Moths dangerous?

The Oak Processionary moth is one to be extremely cautious of. It's not yet reported to be in North Herts, but its presence in Britain is a cause for concern.

Oak Processionary Moth

The Oak Processionary moth was accidentally introduced into the Greater London area in 2005.

It is now classified as an infected area, and we are living inside the large buffer area surrounding it. The Oak Processionary moth is grey striped with a darker head and covered with long white hairs that cause severe irritation, probably needing medical intervention.

As the name implies, they live on oak trees, but can be found on other broad-leaf trees if they have no oak trees. They will be found in web-covered nests on the tree's main branches, not in the leaf canopy.

They come out to feed overnight, returning to the nest to hide and rest through the day. It is unlikely you will spot them until they leave the high branches of the tree, travelling in one behind the other down the main trunk to ground level, where they will continue in their long procession, searching out soft soil to bury into, then pupate and, after a short while emerging as adult moths.

Oak Processionary Caterpillar nest

The nests start off a dull white, turning darker with age and eventually brown, matching the colour of the tree, making it very difficult to identify. If you have any reason to feel that you have discovered one or you see the procession of caterpillars, it is mandatory by law that you notify the local authority North Herts District Council, or Hertfordshire County Council, warn others to stay away and do not touch them; the relevant trained teams will then come out to remove them safely.

Trained safe removal of Oak Processionary caterpillars

Please remember they are not poisonous but they are nasty.

When on holiday on the near continent, you may have been unfortunate to see Pine Processionary moth / caterpillars; these are much the same as Oak Processionary moth and should be left alone and reported. Pine Processionary moths are not known to be in the UK yet, but the south of England has the host trees, and the climate is just what they need to survive, so I imagine it's only a matter of time before they get here.

Pine Processionary Moth

We do have a poisonous moth in the UK; it is doubtful you will eat it and touching it won't kill or make you ill. It is called the Cinnabar moth and is red and black. It feeds on the leaves and flowers of Common Ragwort, building its poison from the poisonous ragwort plant. If you come across yellow and black caterpillars, they will be Cinnabars and will turn into beautiful red and black moths.

Cinnabar moth

From the nasty to the nice

The largest moth in the UK is the Privet Hawk moth. Its caterpillars eat privet, honeysuckle, ash, holly, and garden plants such as spirea and lilac, and the adults feed on the nectar of night-scented flowers such as honeysuckle and jasmine.

Privet Hawk moth

If you find a colossal caterpillar eating your fuchsias, please look after it, as it will most likely be an Elephant Hawk moth. The caterpillar looks like an elephant's trunk, with eye spots to scare off predators.

It is pleasant enough, but the moth is really beautifully coloured pink and gold.

Elephant Hawk moth

In the Garden centre, we have seen the Hummingbird Hawk moth.

Hummingbird Hawk moth

Fun facts

As a young boy, my young sister and I used to hunt along the poplar tree windbreaks for Poplar Hawk moths to keep in a large glass tank our dad found for us; not something mum liked, so it had to go in the shed with our other collections, we had moths everywhere

Poplar Hawk moths

There are over 2600 caterpillars in the British Isles, many using their looks to scare off predators pretending to be other aggressive creatures.

Others give the impression that there will be a nasty smell or taste if attacked or eaten; some actually fight back, wriggling and biting.

The majority use clever disguises to fade into the background; if their disguise fails, a few will drop down on a silk thread, like abseiling, for a quick escape.

Some caterpillars are architects and builders who design self-built homes and hide from the world. Imagine if we had to build our own houses out of leaves and a bit of spit!

Finally, I want to reassure you all that if you don't wash your vegetables well enough and accidentally eat one, you will be ok, as one or two, even three, will not harm you. UK caterpillars don't have enough bacteria or poison within them to cause anything horrible, so enjoy the added protein.

Keep Gardening!


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