Usually appears in compounds: 青蛙 (green frog, the common word for frog), 牛蛙 (bullfrog, a popular food), 蛙泳 (breaststroke, literally "frog swimming"), 井底之蛙 (frog at the bottom of a well = someone with a narrow worldview).
Left 虫 — pictograph of a coiled snake, generalised to all small crawling creatures. As the indexing radical it places 蛙 with small-animal chars: 蛇 snake, 蝌蚪 tadpole, 螺 snail. Frogs are classified under 虫 in the traditional taxonomy via amphibian-and-creature association, not insect status.
Right 圭 supplies the sound — guī drifting to wā through an old k/w alternation visible in this small phonetic family. Same component appears in 娃 baby, 哇 wow, 洼 hollow, 鞋 shoe, all sharing the wā/guī reading. Borrowed purely for sound, with no jade-tablet meaning carried over.
