Swarms of flies; Heb. a mixture of insects or flies, as appears from Psalms 78:45, which were of various kinds, as bees, wasps, gnats, hornets, &c, infinite in their numbers, and doubtless larger and more venomous and pernicious than the common ones were.
Related Commentaries of Exodus 8:21
Exodus 8:21
21 Else, if thou wilt not let my people go, behold, I will send swarmsd of flies upon thee, and upon thy servants, and upon thy people, and into thy houses: and the houses of the Egyptians shall be full of swarms of flies, and also the ground whereon they are.