clear-toned cicada
蜩 centers on a specific kind of cicada known for its clear, ringing tone. The meaning is narrow, referring to this insect rather than a broader concept.
蜩 combines 虫 (insect) with 周, which likely contributes the sound and may relate to the idea of a clear, ringing tone. The exact historical development is uncertain.
The insect radical 虫 on the left tells you it's a bug, and the right side 周 looks like a sound wave spreading out. Picture a cicada on a tree, its clear tone ringing out in circles.
For チョウ, imagine a cicada named Chou whose clear song echoes through the summer air: Chou -> チョウ.