This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蜙 combines 虫 (insect) with 松, which likely contributes the sound. The exact historical development is uncertain.
The insect radical 虫 suggests a bug, and 松 (pine) might hint at a pine-dwelling insect, but the exact meaning is uncertain.
For ショウ, imagine a showy insect on a pine tree: show -> ショウ, and the bug puts on a display.
—