Looks like the young of a grasshopper or cricket and these critters do indeed eat tender plants so they could be the culprit nibbling on your impatiens. Try setting a wad of damp newspaper near the eaten plants and after a few hot days look under the paper to see if you can capture the guilty party feasting on your flowers. The good news is this plague of hoppers can come in waves so you may have a lot one year then few the next as nature restores the balance of insects. Keep growing, Marianne Binetti