This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蛚 combines 虫 (insect) with 列, which likely contributes the sound. The exact historical development is uncertain.
The insect radical 虫 beside 列 suggests a kind of insect, but the specific meaning is unknown.
For レツ, imagine a line of insects marching in a row: the word 'lets' (as in 'lets go') cues レツ, and the insects form a column.
—