Please could someone tell me what insect (I assume) is responsible for this amazing structure and these caterpillars. Is it some sort of egg sack? Thanks.
A Google image search finds this article.
https://www.gloucestershirelive.co.uk/news/gloucester-news/amazing-caterpillar-nest-spotted-gloucestershire-4155433
My google search came up with Lackey Moth caterpillar, or Oak Eggar moth caterpillar (the Lackey is a type of eggar moth too)
Cin J