獸有獸語 Beasts Have Beast Speech
原來那妖精幔天結網，擄住這七般蟲蛭，卻要吃他。古云：「禽有禽言，獸有獸語。」當時這些蟲哀告饒命，願拜為母。遂此春採百花供怪物，夏尋諸卉孝妖精。原来那妖精幔天结网，掳住这七般虫蛭，却要吃他。古云：「禽有禽言，兽有兽语。」当时这些虫哀告饶命，愿拜为母。遂此春采百花供怪物，夏寻诸卉孝妖精。
逐句解 Line by line
The fact was that these monsters had curtained off the sky with their web and caught these seven sorts of crawling thing, meaning to eat them.
幔天結網 — curtaining heaven and knotting a net. 蟲蛭 covers insects and worms together, the low creeping things. They were food before they were sons.
As the ancients said: "Birds have bird speech and beasts have beast speech."
禽有禽言，獸有獸語 is built on a perfect parallel, five characters against five, and the point is that animals can be reasoned with in their own tongue. The saying is doing real work: it explains how a negotiation was possible.
At the time these insects pleaded for their lives and asked to be allowed to bow to them as mothers.
為 is wéi, to be or to serve as — bow to them as mothers, not for their sake. 哀告饒命 is the same plea the seven themselves made in the pool a few passages ago, and got refused.
So from then on they gathered a hundred flowers in spring to supply the creatures, and sought out every plant in summer to serve the spirits dutifully.
供 is gōng, to supply. 孝 is filial duty — the word for what a child owes a parent, and the chapter has already had Eight Rules quote Confucius on exactly that. Seven insects pay it to seven spiders.
The insects were dinner. They begged for their lives, offered to become adopted children instead, and the offer was accepted.
That is the same transaction the seven women were refused half an hour ago. They knelt in the water, pleaded, offered to pay — and Eight Rules answered with a proverb about not trusting sweet talk. The spiders, in the same position, said yes.
The saying about birds and beasts is the hinge, and it is a real one: every creature has a language of its own. It is offered as the explanation for why a negotiation between a spider and a wasp was possible at all, and the book presents it without a flicker of doubt.