Else, if you will not let my people go, behold, I will send swarms of flies upon you, and upon your servants, and upon your people, and into your houses: and the houses of the Egyptians shall be full of swarms of flies, and also the ground on which they are.
All Commentaries on Exodus 8:21 Go To Exodus 8
Isodore of Seville
AD 636
In the fourth place, Egypt is struck with flies. The fly is an insolent and restless animal. What does it stand for except the arrogant concerns of carnal desires? Egypt is struck with flies because the hearts of those who love this world are battered by the disquiet of their desires. The translators of the Septuagint put cynomyia here, which means “dog fly.” This word meant the habits of a dog, in which the pleasures of the mind and the indulgence of the flesh are constantly expressed. By dog fly this passage can also mean the eloquence of lawyers, which they use to tear at one another like dogs. Questions on the Old Testament, Exodus–.