繭 means 'cocoon'

These essays detail complex, interdependent systems, both natural and economic. Sericulture was once so essential to Japan's economy that mulberry (桑) fields are marked on maps, as silkworms eat only mulberry leaves. These animals laboriously spin cocoons (繭), producing filaments that become silk kimonos after many financial transactions. Similarly, Japanese apiarists oversee busy bees (蜂) that make not only hives and honeycomb but also honey to be sold and consumed in multiple ways. Animals build intricate nests and webs (both 巣) that inspire terrific Japanese figurative language. People even eat some nests!