When the fifth trumpet blew (Rev 9), who were the locusts told to hurt?

Only those who don't have God's seal on their foreheads

(But they were not to hurt the trees, grass, or any green thing.)

And there came out of the smoke locusts upon the earth: and unto them was given power, as the scorpions of the earth have power.

And it was commanded them that they should not hurt the grass of the earth, neither any green thing, neither any tree; but only those men which have not the seal of God in their foreheads. Revelation 9:3-4