A proverb meaning that even the smallest or weakest creature has pride or the will to defend itself; do not underestimate others.
相手は経験が浅いが、侮って手を抜くと痛い目に遭うよ。一寸の虫にも五分の魂だからね。
The opponent is inexperienced, but if you underestimate them and slack off you'll suffer. Even a tiny bug has a soul.
彼女は普段おとなしいが、追い詰められると強く反撃する。一寸の虫にも五分の魂だ。
She is usually quiet, but when cornered she fights back fiercely. Even the smallest creature has a will.
この仕事は小さなことでも気を抜けない。一寸の虫にも五分の魂だと心得ている。
You can't let your guard down even on small tasks. I keep in mind that even a tiny bug has pride.