Two of the favourite sampling techniques of the entomologist are sweeping a net through tall grassland and beating low-hanging branches with a net to catch whatever is resting among the leaves. Here are some results from a day recording for the L.R.S. a couple of summers ago to show just what riches can be found with a bit of dedicated beating and sweeping.
Although the virtual location is in the middle of a field suitable for sweeping, you won't find the cache there. To locate it, use these notes.
Assume N51 and W002.
You can validate your puzzle solution with certitude.
I have written a PDF guide to the Dingestow Butterfly cache Series that might be useful for people working out which puzzles to prioritise. I promise it doesn't contain any Hints though.
https://drive.google.com/file/d/1eCgwQKhpjCcAXxTjjhAUnEFyospeDkON/view?usp=sharing