This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蜏 combines 虫 (insect) with 秀, which likely contributes a phonetic element. The exact historical development is uncertain.
The insect radical 虫 beside 秀 suggests a bug, but the meaning is unclear. Picture a mysterious insect with a showy appearance, but its name is unknown.
For ユウ, imagine a unique insect you've never seen before: you -> ユウ, and you wonder what it is.