Yahweh said to me, "Amos, what do you see?" I said, "A plumb line." Then the Lord said, "Behold, I will set a plumb line in the midst of my people Israel. I will not again pass by them any more.
That is, the locusts had made an end of eating the grass of the land, as he saw in the vision the locusts coming in and destroying the green crops completely.