horse botfly larva
Rare term for the larva of a horse botfly (Gasterophilus species). The cross-reference 馬蠅 (うまばえ) refers to the adult fly.
See also: ウマバエ
In old documents, a larva that parasitizes the stomach of horses is recorded under the name 筍虫.
Compound of 筍 (takenoko, 'bamboo shoot') and 虫 (mushi, 'insect'), likely from the larva's shape resembling a bamboo shoot. The exact origin is uncertain.