"David in Normandy" wrote
The netting also help to deter cabbage white butterflies. They like to
lay their eggs under the leaves, and it puts them off if they can't
readily land there. In principle they could climb through the holes,
but this doesn't seem to happen.

I thought the 1cm gauge netting I'd got to save my broccoli from the
feathered menace would also keep off the butterflies off, but the ones
here seem to have some kind of Houdini trick to get right through it and
I still ended up with lacy leaves for the last two years.

--
Sue