Rashi on Genesis 1:20/רש"י על בראשית א׳:כ׳

1נפש חיה LIVING CREATURES — Creatures that shall have vitality.

2שרץ Every living creature that does not rise much above the ground is called שרץ, e. g., of winged creatures — flies; of abominable creatures — ants, beetles and worms; of larger creatures — the mole, snail and others of the same kind, and all fishes.