small green frog, cicada
蟈 centers on small creatures that produce sound: a small green frog or a cicada. Both meanings share the idea of a noisy, diminutive animal.
蟈 combines 虫 (insect/creature) with 國, which likely contributes the sound. The character was used for small, noisy creatures like frogs and cicadas.
The insect radical 虫 beside 國 suggests a tiny creature that makes a loud, country-filling sound: a small green frog or a cicada.
For カク, imagine a small frog croaking "kaku" in a corner of a country garden: kaku -> カク.