Lower down

David Attenborough,The Living Planet,Londres, Reader Digest, 1985, p. 238.

Many species of caddis fly larva live in fresh water. Lower down, in less turbulent rivers and in the still water of lakes, they construct tubes from twigs or sand grains and move gently across the bottom, grazing on leaves and algae ; but up here, where little plant food is to be had, the caddislarvae are hunters, trapping their prey with nets. One species spins a funnel of silk on the underside of a stone and live inside it, grabbing other insect larvae or small crustaceans that might be swept past.