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Spindle Ermine Moths

Robin Holmes sent in some fascinating photos of a bush opposite his house in Forncett St Mary, festooned, almost entirely, in a greyish, silken web.  Inside is a mass of caterpillars munching up the leaves. It is a spindle tree. In Autumn it has lovely pink and orange berries – the four golden orange seeds lapped in the four pink lobes that form the fruit.

2024.03.moths close up copy.Photo Robin Holmes smErmine spindle caterpillars in their webbing protection. Photo: Robin Holmes
 
In his 20th Century herbal Grigson tells us that this wild plant was used for skewers, pegs, viola bows, for the virginal (an early form of the piano) and toothpicks.
The caterpillars are the larvae of the spindle ermine moth that are dependent on this plant. Some of the caterpillars will pupate into a silken cocoon and then emerge as a handsome white moth spotted with black. They are small with a wingspan of 19 – 26 millimetres.
 
Ermine Spindle mothThe adult moth thanks to David Short, Creative Commons, https://www.flickr.com/photos/14583963@N00/23685906363
 
It seems that the moths have evolved this webbing strategy to provide protection from predators by hiding their pupating offspring.  They will look for mates, flying at night from late June to early September. The female will then lay eggs on a spindle bush. Bluetits are fond of the caterpillars that often emerge in time to feed their hatchlings.
In Norfolk we also have the Orchard Ermine and the Apple Ermine.
Do not worry about any of these moths. Do not kill them. They will go and the spindle and other trees will survive. They will probably choose a different bush next time. They function as pollinators and provide food for birds.

 

April 2024

Reference

Geoffrey Grigson, A Herbal of all Sorts, 1959, Phoenix House, London,

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