This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蛽 combines 虫 (insect) with 貝 (shellfish). The exact historical development is uncertain, but it likely refers to some kind of shellfish or insect.
The left side 虫 suggests an insect, and the right side 貝 suggests a shellfish. Picture a small creature that could be either an insect or a shellfish, but its exact identity is unclear.
For バイ, imagine a small bay where both insects and shellfish live: bay -> バイ, and the kanji shows both 虫 and 貝.