Thus the Lord Yahweh showed me: and, behold, he formed locusts in the beginning of the shooting up of the latter growth; and, behold, it was the latter growth after the king's harvest.
The thing to remember about the first two of the visions of threatened disasters against Israel is that they did not occur, but were averted through the prophet's intercession.  The evident reason why Amos included these first two sections in his sermon was that of showing to all the people that he in no manner desired the evil things to come to pass which it was his duty to prophecy, but that he actually stood before God as an advocate of the people and as a prayerful intercessor for their good.  This angle of Amos' prophecy was left out of Amaziah's report to the king.