This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蜯 combines 虫 (insect/creature) with 奉, but the exact historical development is uncertain. It may have originally referred to a type of shellfish or creature, but no clear etymology is established.
The left side 虫 suggests a creature, and the right side 奉 looks like an offering. Imagine an unknown sea creature being offered, but its true nature remains a mystery.
For ホウ, picture a mysterious creature letting out a hollow sound: hollow -> ホウ, echoing from the shell-like shape of 蜯.