According to the book "Revelation It's Grand Climax at Hand!" Chapter 22, the plague of the locust had fulfillment in the first century and the 20 century also. They say that the book of Joel describes a plague of insects, including locusts, that is similar to the one that John sees. It was to cause much discomfort to apostate Israel but would also result in individual Jews' repenting and returning to Jehovah's favor. The first century fulfillment came when the newly annointed 1st century christians were relentlessly preaching. " The individuals who responded received his favor to a remarkable degree. But to the ones who refused the invitation, the first-century christians became like a devastating swarm of locusts."...... "The "plaguing" continued until the "fear inspiring day" in 70 C.E., when Jehovah brought the Roman armies against Jerusalem to destroy it."
The 20th century Plague
"Reasonably, we could expect Joel's prophecy to have a final fulfillment in the time of the end. How true this has proved to be! At the Bible Students' convention at Cedar Point, Ohio, U.S.A, September 1-8, 1919, a notable outpouring of Jehovah's spirit activated his people to organize a global campaign of preaching. Of all professed Christians, they alone, recognizing that Jesus had been enthroned as heavenly King, spared no effort in publishing abroad that good news. Their relentless witnessing, in fulfillment of prophecy, became as a tormenting plague to apostate Christendom.---Matthew 24:3-8, 14; Acts 1:8
Revelation, written some 26 years after Jerusalem's destruction, also describes that plague..............."And the fifth angel blew his trumpet. And I saw a star that had fallen from heaven to the earth, and the key of the pit of the abyss was given him......At Revelation 9:11, John tells us that the locusts have "a king, the angel of the abyss." Both verses must refer to the same individual, since the angel holding the key of the abyss would logically be the angel of the abyss. and the star must symbolize Jehovah's appointed King, since anointed Christians acknowledge only the one angelic King, Jesus Christ.
The account continues: "and he opened the pit of the abyss, and smoke ascended out of the pit as the smoke of a great furnace, and the sun was darkened, also the air, by the smoke of the pit. and out of the smoke locusts came forth upon the earth; and authority was given them, the same authority as the scorpions of the earth have." Scripturally, the "abyss" is a place of inactivity, even of death.... The small band of Jesus' brothers spent a short time in such an "abyss" of relative inactivity at the end of the first world war. but when Jehovah poured out His spirit upon his repentant servants in 1919, they swarmed forth to meet the challenge of the work that lay ahead."
(from here out I'm going to selectively quote parts of the rest of the chapter because it is way to long to put all of it in here.....)
pg. 144 ".......the locust are to harm only those men who do not have the seal of God on their forheads, those in Christendom who claim to be sealed but whose record belies that claim. Thus the tormenting utterences of these modern-day locusts were directed first against the religious leaders of Christendom. How these self assuming men must have been tromented at hearing it publicly announced that not only were they failing to lead their flocks to heaven but they themselves would not get there!............pg 147......The modern day locusts had a job to do, the Kingdom good news had to be preached. Errors had to be exposed, Lost sheep had to be found. As the locust went about these tasks, the world was forced to sit up and take notice........(and finally!) "rather than announce the incoming Kingdom of God, Christendom's clergy have chosen to remain with Satan's world. they want no part with the locust band and their KING, concerning whom John now observes. "They have over them a king, the angel of the abyss. IN Hebrew his name is Abaddon(meaning "destruction", but in Greek he has the name Apollyon (meaning "destroyer'). Revelation 9:11. As 'Angel of the abyss' and 'destroyer' JESUS has truly released a plaguing woe on Christendom.