This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蟸 combines 豕 (pig) with 䖵 (insects). The exact historical development is uncertain, but it may have originally depicted insects associated with pigs or a specific type of insect.
With no clear meaning, picture a pig (豕) covered in insects (䖵) — perhaps a swarm of bugs bothering the animal. This image can help remember the shape, but the actual meaning remains uncertain.
For レイ, imagine a ray of light (レイ) shining on the pig and insects, making them scatter. The ray (レイ) ties the reading to the visual scene.