The Spindle Ermine Moth as the name suggests, has white wings with black spots, like the heraldic ermine colour - the winter coat of a stoat. It is a night flying moth, so unlikely to be seen during a visit to Croome. The caterpillars feed on the spindle plant and the silken web can cover entire bushes (this was just a small example).

Below, you can see one of the caterpillars close up and out of the nest. It appears to be flying, but it is actually suspended from a very thin silk thread. They seem to use these as escape routes out of the nest. In the final photo you can see several of these vertical silk threads spanning large areas of the tree.