A bar next to the species name represents the color of the creature's glow, the size of the organ that causes it to glow, and why it glows. (A key at the bottom of the infographic has symbols for distraction, attraction, and more.) Plenty of species are on here--look at the colossal squid!--but it also seems slightly incomplete, and it's not quite clear why. Some bioluminescent fish don't have colored bars next to their names. Is it because the organs that create the light are too small? Because there's not enough info on those species? Something else? We're not sure.