Do fireflies eat shrimp if not what do they eat?

Yes. That's why shrimp now live in the ocean. They used to fly free in the atmosphere, swooping and soaring majestically through the air. Then the fireflies moved in, using their glowy butt-lasers to zap the poor helpless shrimp out of the sky, then feasting upon the remains. Shrimp were nearly wiped out, but a few survivors managed to make it to the ocean and adapt to live under the sea, where they remain today. Ironically, shrimp nets are equally effective in either environment.