This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蟱 combines 虫 (insect) with 無, which likely contributes a phonetic element. The exact historical development is uncertain.
The insect radical 虫 beside 無 suggests a creature, but without a clear meaning, picture a mysterious bug that defies description.
For ボウ, imagine a bow-tied bug: bow -> ボウ, and the insect 虫 wears a tiny bow tie.