noun
blowfly larva; green bottle fly larva; maggot used as bait
Specifically the larva of blowflies or green bottle flies, often used as fishing bait.
釣り餌にサシを使う。
I use blowfly larvae as fishing bait.
サシは肉にたかることがある。
Blowfly larvae sometimes swarm on meat.
うじ is a general term for maggots, while サシ specifically refers to blowfly or green bottle fly larvae, especially in a fishing context.
The origin is uncertain. The kanji 蠁子 is rare and likely a specialized entomological or historical spelling.