大の虫を生かして小の虫を殺す
(Dai no mushi wo ikashite shou no mushi wo korosu;
“Let the large bug live, and kill the small”)

Definition:

Sacrificing small considerations so that the large may survive. Cutting off a part so that the whole may live, as in amputations. A gambit. Triage.

Breakdown:

We have another pair of parallel phrases. The first begins with the noun 大 (dai), “large.” (Yes, it’s functioning as a noun. We know this because:) This is connected by the associative particle の (no) to the noun 虫 (mushi), a generic term for creepy-crawlies most closely associated with insects. This noun phrase is made into the object of a verb by the particle を (wo); the verb is 生かす (ikasu), a transitive verb meaning “to keep something alive” or “to let something live.” The verb is in conjunctive form, allowing it to connect to the second half of the saying. The latter follows the same pattern except that it replaces 大 with 小 (shou), “small,” and 生かす with 殺す (korosu), “to kill,” in sentence-final form.

Notes:

A close variant switches the order and “saves” the large insect rather than merely letting it live: 小の虫を殺して大の虫を助ける (Shou no mushi wo koroshite dai no mushi wo tasukeru).

Example sentence:

「引っ越しなんていやだなぁ。荷造りのために物を捨てるのは取捨選択というより、大の虫を生かして小の虫を殺すことが繰り返すばかりって感じ」

(“Hikkoshi nante iya da naa. Nidzukuri no tame ni mono wo suteru no wa shushasentaku to iu yori, dai no mushi wo ikashite shou no mushi wo korosu koto ga kurikaesu bakaritte kanji.”)

[“Man, I really hate moving. Throwing things away before packing feels less like ‘sorting’ and more like just ‘letting some die so that others may live’ over and over again.”]