The treeworm is a split from the lobed solarworm and replaced the stiltleg sunworm in the Flisch Marsh area. Its photosynthesis has improved a lot and suffices to feed the worm. So it became almost a plant. Because it can burn much more oxygen than plants and thus has more energy, it maintains its ability to move, which it uses in rare cases, for example, when a barrier blocks out the sun. Also it moves very slowly. With its long tongue it sucks out the nutrients out of the earth just like plants' roots. It replaced the stiltleg sunworm, because it was much more efficient at photosynthesis than the sunworm. Unlike its ancestor, it can't flap with its wings.