There remained not one. — The sudden and entire removal of a plague like this at the word of Moses was almost as great a miracle as its sudden coming at his word, and is therefore, when it happened, carefully recorded. (See Exodus 10:19.) It seems not to have happened with the frogs (Exodus 8:11-13) or with the mosquitoes.
Related Commentaries of Exodus 8:31
Exodus 8:31
31 And the LORD did according to the word of Moses; and he removed the swarms of flies from Pharaoh, from his servants, and from his people; there remained not one.