Lid question

so I have a screen lid on my tank. I've heard people say to put saran wrap over it. but would the crab still be able to breathe? I soraya the tank when I notice the water is evaporating, but if I put saran wrap over it, will I need to poke any holes? I don't want the lil guy to suffocate :( and I know they have gills, but I thought they needed air too