Bottom
虫 — the indexing radical, meaning a small creature: insect, reptile, or worm. Anchors
蛋 as an egg laid by such creatures (snakes, lizards, and birds were all classed under
虫 in old usage). From the literal egg came the round-thing extension and the colloquial idiot insult (
笨蛋). Same family:
蛇,
蚊,
蝶.