Butterfly eggs

I have just put some of my tender plants out for an airing, as it has been relatively mild. I noticed several of the orchids (Slipper and Cymbidium) as well as a Clivia had butterfly eggs underneath the leaves. Never seen them this early before. Perhaps they overwintered.

Any advice welcome. I'm reluctant to cut off the leaves, as this will prejudice flowering or use chemicals, but these are expensive plants and I don't want them eaten by caterpillars. I thought of just wiping them off with a damp cloth. Relatively environmentally friendly, but will it work? I doubt if I would get all of them, maybe I'm not intended to.