This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蟟 combines 虫 (insect) with 尞, which likely contributes the sound. The exact historical development is uncertain.
The insect radical 虫 suggests a bug, and the right side 尞 looks like a complex shape. Picture a rare, hard-to-identify insect hiding among tangled brush.
For リョウ, imagine a rare insect named 'Ryo' that only appears in old forests: Ryo -> リョウ.