The Rule of Prey

From Ubik, by Philip K. Dick:

“One insect learns to fly, so another learns to build a web to trap him. Is that the same as no flight? Clams developed hard shells to protect them; therefore, birds learn to fly the clam up high in the air and drop him on a rock. (…) Balance, the full circle, predator and prey. It appears to be an eternal system; and, frankly, I can’t see how it could be improved.”