Explain the phrase, “something flittered there in front of his mind like a bat’s wing” when Ralph yelled at the boys for rolling the rocks?
In my opinion, Ralph is getting completely frustrated at this point, he just received a major cut on his arm and is trying to stop the bleeding, he's looking for Jack and can't find him, and the boys are fooling around. After all of Ralph's attempts to be a leader, after every moment of seeing what needs to be done and trying to get it done, I think this moment demonstrated him being about to lose it. When you keep track of so many things in your mind, you are bound to loose concentration, there is just too much to keep track of. He is holding it together for the most part.
OR, Ralph is going savage. It just may be that sanity is leaving him just like the boys' discipline. It is one of those moments in time where he might have just about let go of caring about leading. This phrase suggests a fleeting nature. Ralph's sense and good nature might be getting ready to leave him.