“For they covered the face of the whole earth, so that the land was darkened [chashak]; and they did eat every herb of the land, and all the fruit of the trees which the hail had left: and there remained not any green thing in the trees, or in the herbs of the field, through all the land of Egypt.” (Exodus 10:15)
Chashak means to withhold light. The locusts' swarm was so thick it blocked sunlight. These locusts ate everything green which had not been destroyed by the hail. This is unlike the locusts of the 5th trumpet who were commanded “that they should not hurt [adikeo] the grass of the earth, neither any green thing, neither any tree; but only those men which have not the seal of God in their foreheads.” (Rev. 9:4) This is a big clue that these are not typical locusts.
Our first clue is that the locusts of today came from the smoke of the abyss (Rev. 9:2-3) and are commanded by a 'fallen star' king who opened the abyss (Rev. 9:1,11) Natural locusts have no king (Proverbs 30:27) Today's locusts are “given power, as the scorpions of the earth have power” (Rev. 9:3).
During their exodus, the children of Israel were led through wilderness containing fiery serpents and scorpions (Deut. 8:15). The Middle East has several different venomous scorpions which cause human deaths every year. Scorpions of the earth have power to sting and inject venom which paralyzes or kills their prey, but God commands these locust-scorpions to not kill yet to torment a particular people group who are not sealed with God's Holy Spirit (Rev. 9:4-5).
God equated scorpions with rebels.
“And you, son of man, be not afraid of them, neither be afraid of their words, though briers and thorns be with you, and you do dwell among scorpions: be not afraid of their words, nor be dismayed at their looks, though they be a rebellious house.” (Ezekiel 2:6)
God gave this command to Ezekiel along with a scroll which he ate and tasted sweet (Ezek. 2:8-3:4), but then later became bitter when he had to prophesy (Ezek. 3:14-17). This is similar to the scroll John was asked to eat after God revealed the seven thunders to him and before He sent him to prophesy (Rev. 10:8-11)
Jesus associated scorpions with Satan, and gave His disciples power over them.
“And he said to them, I beheld Satan as lightning fall from heaven. Behold, I give to you power to tread on serpents and scorpions, and over all the power of the enemy: and nothing shall by any means hurt [adikeo] you." (Luke 10:18-19)
Adikeo is to be unjust, that is, (actively) do wrong (morally, socially or physically): - hurt, injure, be an offender, or be unjust (Strong's). Christians are protected by Christ's promise in Luke and in Revelation that these scorpion rebels will not hurt us.
Amos saw a vision of grasshoppers come upon the land, but interceded, and the Lord relented and did not bring it upon king Jeroboam II of Israel (Amos 7:1-3). The prophet Joel predicted a plague of locusts during the reign of king Uzziah of Judah which did occur. In Joel 1:4, some scholars assume Joel was describing the four growth stages of locusts. After hatching from the egg, a nymph is called a hopper; what most of us recognize as the green grasshopper. But after heavy rains when lots of green vegetation exists, solitary grasshoppers can change into gregarious locusts. Green nymphs change to yellow and black locusts, immature adults change from brown to red locusts, and mature adults change from brown to yellow locusts. The coasts of the Red Sea are their natural breeding grounds.
In Joel 2:2, the plague of locusts is now a plague of “people” who blot out the sun (Joel 2:10). The people of Judah heeded Joel's warnings and fasted and prayed for deliverence from such an army; whereas the people of Israel did not heed Amos, and were taken away into captivity.
“For a nation is come up on my land, strong, and without number, whose teeth are the teeth of a lion, and he has the cheek teeth of a great lion.” (Joel 1:6)
“. . . and their teeth were as the teeth of lions.” (Rev. 9:8)
The Sunni “beast of the sea” has the “mouth of of a lion” (Rev. 13:2); it “had great iron teeth: it devoured and broke in pieces (Daniel 7:7).
“The Mahometans speak much of God being the Maker of locusts; they say he made them of the clay which was left at the formation of Adam; and represent him saying, I am God, nor is there any Lord of locusts besides me, who feed them, and send them for food to the people, or as a punishment to them, as I please: they call them the army of the most high God, and will not suffer any to kill them.” (John Gill's Bible Commentary) I have not been able to verify this.
“The appearance of them is as the appearance of horses; and as horsemen, so shall they run. Like the noise of chariots on the tops of mountains shall they leap, like the noise of a flame of fire that devours the stubble, as a strong people set in battle array. Before their face the people shall be much pained: all faces shall gather blackness." (Joel 2:4-6)
“And the shapes of the locusts were like to horses prepared to battle; and on their heads were as it were crowns like gold, and their faces were as the faces of men. . . . And they had breastplates, as it were breastplates of iron; and the sound of their wings was as the sound of chariots of many horses running to battle.” (Rev. 9:7-9)
Though John never quoted the Old Testament directly in Revelation, he indirectly quoted it or alluded to it. Both of them tell us about this final battle prior to the LORD's return.
“I will also gather all nations, and will bring them down into the valley of Jehoshaphat, and will plead with them there for my people and for my heritage Israel, whom they have scattered among the nations, and parted my land. . . . Assemble yourselves, and come, all you heathen, and gather yourselves together round about: thither cause your mighty ones to come down, O LORD. Let the heathen be wakened, and come up to the valley of Jehoshaphat: for there will I sit to judge all the heathen round about. Put you in the sickle, for the harvest is ripe: come, get you down; for the press is full, the fats overflow; for their wickedness is great. Multitudes, multitudes in the valley of decision: for the day of the LORD is near in the valley of decision. The sun and the moon shall be darkened, and the stars shall withdraw their shining. The LORD also shall roar out of Zion, and utter his voice from Jerusalem; and the heavens and the earth shall shake: but the LORD will be the hope of his people, and the strength of the children of Israel. So shall you know that I am the LORD your God dwelling in Zion, my holy mountain: then shall Jerusalem be holy, and there shall no strangers pass through her any more.” (Joel 3:2, 11-17)
“For they are the spirits of devils, working miracles, which go forth to the kings of the earth and of the whole world, to gather them to the battle of that great day of God Almighty. Behold, I come as a thief. Blessed is he that watches, and keeps his garments, lest he walk naked, and they see his shame. And he gathered them together into a place called in the Hebrew tongue Armageddon. And the seventh angel poured out his vial into the air; and there came a great voice out of the temple of heaven, from the throne, saying, It is done. And there were voices, and thunders, and lightning; and there was a great earthquake, such as was not since men were on the earth, so mighty an earthquake, and so great. And the great city was divided into three parts, and the cities of the nations fell: and great Babylon came in remembrance before God, to give to her the cup of the wine of the fierceness of his wrath." (Rev. 16:14-19)
“For Israel has not been forsaken, nor Judah of his God, of the LORD of hosts; though their land was filled with sin against the Holy One of Israel. Flee out of the middle of Babylon, and deliver every man his soul: be not cut off in her iniquity; for this is the time of the LORD's vengeance; he will render to her a recompense. Babylon has been a golden cup in the LORD's hand, that made all the earth drunken: the nations have drunken of her wine; therefore the nations are mad. Babylon is suddenly fallen and destroyed: howl for her; take balm for her pain, if so be she may be healed. We would have healed Babylon, but she is not healed: forsake her, and let us go every one into his own country: for her judgment reaches to heaven, and is lifted up even to the skies. The LORD has brought forth our righteousness: come, and let us declare in Zion the work of the LORD our God.” (Jeremiah 51:5-10)
The locusts of the 5th trumpet are swarms of Muslim rebels upon whom the LORD will have His vengeance.