noun
horse botfly
A parasitic fly (Gasterophilus intestinalis) whose larvae infest the stomach of horses. The name literally means 'horse fly', but it is distinct from the common horsefly (アブ).
ウマバエの幼虫は馬の胃に寄生する。
The larvae of the horse botfly parasitize the stomach of horses.
牧場でウマバエを見かけた。
I saw a horse botfly at the ranch.
アブ is the common horsefly (family Tabanidae), a biting fly that feeds on blood, while ウマバエ is a botfly whose larvae are internal parasites of horses.
Compound of 馬 (uma, 'horse') + 蠅 (hae, 'fly'). The kanji 蝿/蠅 are rarely used; the word is normally written in kana.