'Gadflies' in the Bible

For if you do not let My people go, hear this: I will send swarms of [bloodsucking] insects on you and on your servants and on your people and into your houses; and the houses of the Egyptians will be full of swarms of insects, as well as the ground on which they stand.

But on that day I will separate and set apart the land of Goshen, where My people are living, so that no swarms of insects will be there, so that you may know [without any doubt] and acknowledge that I, the Lord, am in the midst of the earth.

Then the Lord did so. And there came heavy and oppressive swarms of [bloodsucking] insects into the house of Pharaoh and his servants’ houses; in all the land of Egypt the land was corrupted and ruined because of the [great invasion of] insects.

Moses said, “I am going to leave you, and I will urgently petition (pray, entreat) the Lord that the swarms of insects may leave Pharaoh, his servants, and his people tomorrow; only do not let Pharaoh act deceitfully again by not letting the people go to sacrifice to the Lord.”

The Lord did as Moses asked, and removed the swarms of [bloodsucking] insects from Pharaoh, from his servants and from his people; not one remained.