It is better to call the old leaves of silkworm inexhaustible than to call them exhausted.
Eating whales: eating them step by step like silkworms eating mulberry leaves, and swallowing them at once like whales. It is a metaphor for occupying and annexing the territory of other countries in various ways.
Silkworm-headed dovetail: It describes that calligraphy is dignified and light with a pen.
Bird Road in Can Cong: refers to the steep mountain road.
Silkworm and crab Kuang: Kuang: back shell. Metaphor is real, and the two are irrelevant.