This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蜼 combines 虫 (insect/reptile) with 隹, which may be a phonetic component. The exact historical development is uncertain.
The insect radical 虫 beside 隹 suggests a creature, but the exact meaning is unclear. Picture a strange bug with a bird-like tail (隹) to remember its shape.
For イ, imagine an eagle (イーグル) swooping down to catch the insect: eagle -> イ, and the bug tries to flee.