This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蝲 combines 虫 (insect) with 剌, which likely contributes the sound. The exact historical development is uncertain.
The insect radical 虫 suggests a bug-related meaning, but without clear English meanings, picture a strange insect with a sharp, thorny appearance like the right side 剌.
For ラツ, imagine a bug that makes a sharp 'rats!' sound when you see it: rats -> ラツ, and the insect scurries away.
red swamp crayfish (Procambarus clarkii)