The Spindle and the Moth - June 2025

In our pocket woodland on the edge of the garden, we have sadly lost 2 of the 5 native trees, but amongst the 3 remaining ones is a species that goes by the name of Euonymus europeus, or the Common Spindle.

It is a small, deciduous, bushy tree, and in the wild, is often an indicator of ancient woodland. Its flowers are fairly inconspicuous, being a greenish white colour. They occur in clusters in May and early June, and each flower is hermaphrodite, having both female and male productive parts. They rely mainly on insects for pollination, but can selfpollinate if needs be.

But this tree really comes into its own in the autumn. Its leaves turn a glorious orangey-red and it has bright pink fruits which open to reveal orange seeds (see photo below).

However, this spring you may have noticed that our spindle had a few small silken sheets draped within the foliage... modest on the scale seen on some bushes, which are absolutely covered in what look like a forest of cobwebs. Inside these webs are many small caterpillars, which are pale coloured and have a dark spot either side of each segment. These are the caterpillars of the Spindle ermine moth (Yponomeuta cagnagella).

According to the Butterfly Conservation Trust, the production of so many offspring is an evolutionary survival strategy; safety in numbers. But the downside is that, unless protected, such a huge number of caterpillars would be bound to draw the attention of predators. So, the caterpillars produce these webs inside which they gorge on the leaves of their host plant, in this case Spindle. These larvae have overwintered and following a number of moults, will pupate.

The moths themselves take to the wing around late June and are named for their resemblance to ermine; they have white wings with black spots. There are actually 8 species of ermine moth in the UK, generally named after their host plant. Having emerged and mated, the adult moth will lay its eggs on their chosen species, to start the cycle once more.

The webs, having served their purpose, disintegrate, and usually expose a plant with severely depleted leaf cover. This doesn't generally cause long term damage and the foliage will recover. But our Spindle appears to have got off very lightly, with little evidence of leaf loss. This could be because it was a fairly light infestation, or could there have been something else at play?

A couple of the photographs I took show a larger black caterpillar which appears to be predating the small ones. Is it the ermine caterpillar in its final moult, before it pupates? And are the discarded skins those that have been left after moulting, or the discarded remnants following predation by an unidentified intruder? If anyone out there has the answer, then please let us know!

Meanwhile I urge you to look out for this gorgeous little tree in the autumn; it's a picture!

Words and pictures: Denise Long June 2025