The Citoac are a sapient but non-technological species of plant-like lifeforms native to the rainforests of the planet Nasat. They are mobile creatures with slender leaf-like limbs and pseudopod-like feet, which obtain nourishment by both photosynthesis and predation. They produce a highly acidic substance which enables them to quickly kill fauna or damage the tissues of large tree-like flora. They communicate solely by telepathy.
Historically, the Citoac have been a relatively peaceful civilization, uninterested in technology. When the Nasat, a crustaceanoid sapient species of their homeworld, started building cities on the tree tops, they threatened the Citoac's supply of light, which they needed for photosynthesis, and thus war emerged between the two species. The conflict ended with the signing of the Citoac-Nasat treaty which declared the lower levels of the forest as Citoac territory, and the upper levels as Nasat territory as long as the Nasat built their settlements in a way not prejudicial to the Citoac and the forest at large.
- Star Trek: Starfleet Corps of Engineers series, book 27 - Balance of Nature, by Heather Jarman