As I mentioned, flies is not in the Hebrew. The only word is “swarm” which is arob in Hebrew. Though it is true practically all other translations use the word “flies”, a swarm of beetles is as reasonable as a swarm of flies.
There is also no mention in the text of livestock being tortured in any translation. The only thing mentioned is an abundance of them. So an abundance of any insect would be a nuisance.
Exod 8:20-22 (KJV)
20 Then the LORD said to Moses, “Rise up early in the morning and present yourself to Pharaoh, as he goes out to the water, and say to him, ‘Thus says the LORD, “Let my people go, that they may serve me.
21 Or else, if you will not let my people go, behold, I will send swarms of flies on you and your servants and your people, and into your houses. And the houses of the Egyptians shall be filled with swarms of flies, and also the ground on which they stand.
22 But on that day I will set apart the land of Goshen, where my people dwell, so that no swarms of flies shall be there, that you may know that I am the LORD in the midst of the earth.
Exod 8:20-22 (YLT)
20 And Jehovah saith unto Moses, ‘Rise early in the morning, and station thyself before Pharaoh, lo, he is going out to the waters, and thou hast said unto him, Thus said Jehovah, Send My people away, and they serve Me;
21 for, if thou art not sending My people away, lo, I am sending against thee, and against thy servants, and against thy people, and against thy houses, the beetle, and the houses of the Egyptians have been full of the beetle, and also the ground on which they are.
22 ‘And I have separated in that day the land of Goshen, in which My people are staying, that the beetle is not there, so that thou knowest that I am Jehovah in the midst of the land,