What fire consumed before it, and what flame burned after it?
Rashi: They destroy everything as if fire consumes in front of them "and a flame burns in back of them."
Radak: The verse discusses in front of and in back of the locusts, for the place where they camped could not be seen; they covered the land. They camped here, and eat and travel elsewhere.
Malbim: The verse depicts that they eat and eradicate all trees and vegetation like a burning fire. When it left, they did not leave anything to eat, like a flame that burns the roots and ground after the fire.
What is the comparison to Gan Eden?
Rashi: The land was like Gan Eden (Malbim - full of all good) before they came, and they left it "like a desolate Midbar."
Why does it add "v'Gam Peleitah Lo Haysah Lo"?
Radak: It did not leave any vegetation that it did not eat.
Radak citing Targum Yonasan: There is no shelter for Resha'im.
Malbim: There is a remnant that people save from a fire; here, they did not save anything.
