Insect radical on the left, the indexing component. In classical Chinese
虫 covered all small wriggling animals - bugs, snakes, lizards, amphibians. It places
螈 alongside other reptile/amphibian chars
蛇 snake,
蛙 frog,
蜥 lizard, where the
虫 stretches well past 'insect' in the strict modern sense.