Locust plague really an alien invasion????

LUKE 8:26 Then they sailed to the country of the Gadarenes, which is opposite Galilee. 27 And when He stepped out on the land, there met Him a certain man from the city who had demons for a long time. And he wore no clothes, nor did he live in a house but in the tombs. 28 When he saw Jesus, he cried out, fell down before Him, and with a loud voice said, "What have I to do with You, Jesus, Son of the Most High God? I beg You, do not torment me!" 29 For He had commanded the unclean spirit to come out of the man. For it had often seized him, and he was kept under guard, bound with chains and shackles; and he broke the bonds and was driven by the demon into the wilderness. 30 Jesus asked him, saying, "What is your name?" And he said, "Legion," because many demons had entered him. 31 And they begged Him that He would not command them to go out into the abyss [abusson]. 32 Now a herd of many swine was feeding there on the mountain. So they begged Him that He would permit them to enter them. And He permitted them. 33 Then the demons went out of the man and entered the swine, and the herd ran violently down the steep place into the lake and drowned. (NKJV)
As the Scripture above shows, the demons who inhabited this man were terrified of being banished by Christ into "the Abyss." What is this Abyss? The Jewish New Testament Commentary says of this place mentioned in Luke 8:31:

The bottomless pit, Greek abussos, 'abyss,' found also at Ro 10:7; Rv 9:1-2, 11; 11:7; 17:8; 20:1, 3. The word is used in the Septuagint to translate Hebrew tehom, as in Genesis 1:2, 'Darkness was over the abyss.' At a later period in Judaism 'tehom' referred to the place where renegade spirits were confined" (p. 119).
Regarding the Abyss, The Zondervan Pictorial Bible Dictionary says:

In classical Greek ábyssos was an adjective meaning 'bottomless,' applied to the primeval deep of ancient cosmogonies, an ocean surrounding and under the earth. In the LXX it translates Heb. tehôm meaning the primal waters of Genesis 1:2, once the world of the dead (Ps. 71:20). In later Judaism it means also the interior depths of the earth, and the prison of evil spirits. . . . In Luke 8:31 the demons fear the primal prison deep more than the known depth of the Lake of Galilee. In Revelation the horror of infinite deeps is intensified ("Abyss," p. 8).
In the end-time prophecy recorded by John in the book of Revelation, the Abyss plays a large part in the events leading up to the return of the Messiah. During the period of the "seven trumpets," which mark the pouring out of God's wrath on an unrepentant mankind, the Abyss is opened at the sounding of the fifth trumpet.

REVELATION 9:1 Then the fifth angel sounded: And I saw a star fallen from heaven to the earth. To him was given the key to the bottomless pit [abussou]. 2 And he opened the bottomless pit [abussou], and smoke arose out of the pit like the smoke of a great furnace. So the sun and the air were darkened because of the smoke of the pit. 3 Then out of the smoke locusts came upon the earth. And to them was given power, as the scorpions of the earth have power. 4 They were commanded not to harm the grass of the earth, or any green thing, or any tree, but only those men who do not have the seal of God on their foreheads. 5 And they were not given authority to kill them, but to torment them for five months. Their torment was like the torment of a scorpion when it strikes a man. 6 In those days men will seek death and will not find it; they will desire to die, and death will flee from them. 7 The shape of the locusts was like horses prepared for battle. On their heads were crowns of something like gold, and their faces were like the faces of men. 8 They had hair like women's hair, and their teeth were like lions' teeth. 9 And they had breastplates like breastplates of iron, and the sound of their wings was like the sound of chariots with many horses running into battle. 10 They had tails like scorpions, and there were stings in their tails. Their power was to hurt men five months. (NKJV)
The unlocking of the Abyss releases a horde of depraved demons upon mankind. God uses them as an instrument of His wrath for five months; they are allowed to torment those on the earth who don't have God's seal on their foreheads (Rev. 7:2-8).

In his commentary on Revelation 9:1, 3, Daniel H. Stern writes:

1 The star is not Satan (despite Isaiah 14:12, Lk 10:17), but an angel, who still has the key at 20:1. The Abyss is not Sh'ol (as at Ro 10:7), but a place where demonic beings are imprisoned (vv. 2-11, 11:7, 17:8, 20:2-3). In the Apocrypha, God is called, "You who close and seal the Abyss with your fearful and glorious name"
3 Demonic monsters are released which fly like locusts (Exodus 10:12-20; Joel 1:4, 2:4-14) and sting like scorpions (Ezekiel 2:6, Lk 11:12) (Jewish New Testament Commentary, pp. 815, 816).

In Revelation 9:11, a mysterious character is introduced into the story. He is released from the Abyss along with the multitude of demons, and is identified as their king or ruler.

REVELATION 9:11 And they had as king over them the angel of the bottomless pit [abussou], whose name in Hebrew is Abaddon, but in Greek he has the name Apollyon. (NKJV)
This Abaddon (which is Hebrew for "destroyer") is the demonic ruler of the Abyss. Abaddon is the highest ranking evil angel now confined in the Abyss. Although not specifically mentioned by these names anywhere else in the Bible, Abaddon plays a major role in the events at the end of this current age.

After the release of the demons from the Abyss, another group of evil spirits is released onto the earth.

REVELATION 9:13 Then the sixth angel sounded: And I heard a voice from the four horns of the golden altar which is before God, 14 saying to the sixth angel who had the trumpet, "Release the four angels who are bound at the great river Euphrates." 15 So the four angels, who had been prepared for the hour and day and month and year, were released to kill a third of mankind. 16 Now the number of the army of the horsemen was two hundred million; I heard the number of them. 17 And thus I saw the horses in the vision: those who sat on them had breastplates of fiery red, hyacinth blue, and sulfur yellow; and the heads of the horses were like the heads of lions; and out of their mouths came fire, smoke, and brimstone. 18 By these three plagues a third of mankind was killed -- by the fire and the smoke and the brimstone which came out of their mouths. 19 For their power is in their mouth and in their tails; for their tails are like serpents, having heads; and with them they do harm. 20 But the rest of mankind, who were not killed by these plagues, did not repent of the works of their hands, that they should not worship demons . . . (NKJV)
In this passage of Scripture, we see that to further punish those who will not obey Him, God authorizes the release of four powerful demons who have been held for just this occasion. Their mission is the destruction of 1/3 of mankind. To accomplish this feat, they are given an army of 200 million evil spirits. Just as Christ and his angelic army later ride white horses (Rev. 19:11, 14), these demons also ride "horses." Fire, smoke, and brimstone issue from the mouths of their horses, and with these plagues possibly a billion and a half people are killed.

Both Abaddon, the evil spirit currently ruling over the Abyss, and the four angels now "bound at the great river Euphrates" appear to be high-ranking and powerful demons. Many biblical passages allude to the fact that both good and evil angels have different levels of authority.