Homo erectus represents a different kind of hominin than the more ancient african predecessors. one of the reasons is

One of the reason is : An increased body size and robustness. They have long spatial/temporal range , they were the first hominin to leave Africa, they have modern human body proportions , they were the first to have a protruding human nose and they actively were hunting.

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.