Several years ago a couple of sections of hedge near here appeared to have been wrapped in the biggest cobweb I had ever seen. The sections were about 3-4 meters long — the length of a farm gate. At first I thought it was something to do with planning permission — as when farmers or developers wrap a section of hedge in green plastic netting to stop birds from nesting while they wait for permission to root it out for a new entry. Closer examination revealed something more interesting!
The net appeared to be a huge, quite robust, cocoon in the safety of which thousands of caterpillars were devouring the hedge.
Apocalyptic!” thought I, “That’s the end of that hedge and maybe life as we know it.”
But no, that section which was mainly bird cherry looked dead but the web eventually disappeared and the hedge recovered.
This year the phenomenon has recurred, this time in a hedge that is mainly holly with bird cherry growing through it and the caterpillars of the Bird Cherry Ermine Moth (Yponomenta evonymella), for these are the culprits, have ensheathed most of the bird cherry but left the holly unscathed.
The caterpillars are thriving protected from predatory birds and they appear to have eaten much of the foliage within their web nests already but below you can see them spinning new web to enclose more food.
Now we must wait for them to pupate and later for the adult moths to emerge — a ghostly white night-flyer with rows of black dots, an echo of the caterpillars…
They are successful as a species — they’ve developed a clever biodegradable protective wrapper for themselves and they don’t even appear to come back to the same trees twice, they protect their food source — little eco-warriors.