Set in a far future, the earth has locked rotation with the Sun, and is attached to the now-more-distant Moon, which resides at a Trojan point, with cobwebs spun by enormous spider-like plants. The Sun has swollen to fill half the sky and, with the increased light and heat, the plants are engaged in a constant frenzy of growth and decay, like a tropical forest enhanced a thousandfold. The plants many now omnivores have filled all the ecological niches on the land and in the air, many evolving primitive nervous systems and, in some cases, eyes; of the animals in the forest only the descendants of four species of social insects remain - tigerflies (evolved from wasps), tree-bees, plant-ants and termights (from termites) - along with small groups of humans (a fifth of the size they are now); all other land and air animals have been driven to extinction by the vegetable kingdom, apart from a few shore dwellers. The humans live on the edge of extinction, within the canopy layer of a giant banyan tree that covers the continent on the day side of the earth.