God, it seems, gave him no warning, because he showed himself in the very last plague to be both perfidious and incorrigible. Others think he was forewarned, though that be not here expressed. Lice, so the Hebrew word is rendered by all the Jewish and most other interpreters. But it is probable that what is said of the locusts, Exodus 10:14, was true of these, that they were much more loathsome and troublesome than ordinary.
Related Commentaries of Exodus 8:16
Exodus 8:16
16 And the LORD said unto Moses, Say unto Aaron, Stretch out thy rod, and smite the dust of the land, that it may become lice throughout all the land of Egypt.