Matthew Poole and continuators on Exodus 10:12

12 And the LORD said unto Moses, stretch out thine hand over the land of Egypt for the locusts, that they may come up upon the land of Egypt, and eat every herb of the land , even all that the hail hath left.

This is no unusual Plague in Africa and Arabia, where, when the harvest is ripe, they frequently come in vast numbers and eat up all their Corn, and what they do not eat they infect with their touch and the moisture coming from them, and afterwards dying in great numbers they poison the Air and cause a pestilence. So that it is no wonder that Pharaoh and his Servants were so concerned for this Plague, so well known to them, especially considering, that this was like to be far worse then all of the same kind which they had either seen or heard of.