getting closer but it still doesn't look right.

This is the thing I don't like about studies, is that aside from the difficulty of even copying a piece, how am I supposed to learn from it? Like, ok, so they lit up the wing. But why? The light source is behind the wing, so shouldn't the wing be dark except for the edge? Presumably there's enough light bounce to light it up anyway, but where is it bouncing off of? everything else in the image is nearly pitch black and wouldn't bounce light. I don't understand.