And it shall come to pass in that day, that the LORD shall hiss for the fly that is in the uttermost part of the rivers of Egypt, and for the bee that is in the land of Assyria.
The Lord shall hiss-whistle to bring bees to settle (note, Isaiah 5:26).
For the fly - found in numbers about the arms of the Nile, and the canals from it (Isaiah 19:5-7; Isaiah 23:3), here called "rivers." Hence, arose the plaque of flies (Exodus 8:21). Figurative for numerous and troublesome foes from the remotest parts of Egypt-e.g., Pharaoh-necho, who slew King Josiah at Megiddo, when the latter went against him, because the Egyptian king was going up against the King of Assyria (2 Kings 23:29-30).
And for the bee (Deuteronomy 1:44; Psalms 118:12) - as numerous in Assyria as the fly in marshy Egypt. Sennacherib, Esarhaddon, and Nebuchadnezzar fulfilled this prediction.