Whatever kind of insect is referred to, little matter, as the point is the effect produced and the result. The ground, houses, people and king were covered with the destroying creatures. In the first plague "the river stank," in the second "the land stank." Under this terrible visitation "the land was corrupted" or "destroyed." In a country like Egypt, where idolatry of the most debasing character was universally practiced, where certain kinds of insects as the beetle were adored and worshipped, this judgment must have produced dismay and terror amongst the Egyptians.
Sources: la93511