Caterpillars are something you will usually stumble across by accident, although if you know which ones go on which plants at the right time of year you can have more luck. It is not just butterflies than have caterpillars, I've seen them from moths, beetles and flies. In fact the most common ones to find are from moths.

Croome being so rich in bird life means the poor caterpillars will get eaten unless they can find cover soon after hatching. This is probably why I've only found some of these caterpillars just after they have emerged from their silken nests. The pleasure gardens and shrubberies are good places for caterpillars to feed (much to the annoyance of the gardeners no doubt).