This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蚚 combines 虫 (insect) with 斤, but the historical role of 斤 is uncertain. It may be a phonetic component, but the exact origin is unclear.
The left side 虫 suggests an insect, and the right side 斤 looks like an axe. Imagine a tiny insect with axe-like mandibles, but its exact meaning is uncertain.
For キ, picture a key-shaped insect: key -> キ, and the insect 虫 holds the key 斤.