This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 蠺 is uncertain. It visually contains 日 and 䖵 (two insects), but the original semantic and phonetic roles are unclear.
With no clear meaning, focus on the shape: 日 (sun) over 䖵 (two insects). Imagine two insects basking under the sun, but what they represent is a mystery.
For サン, picture the sun (サン) shining down on the two insects: sun -> サン, tying the reading to the visible 日 component.