Symbolism, Imagery, Allegory
Do you write about every bug you see? Neither does Hemingway. That should be your first clue that the grasshopper means something more than a grasshopper. To be fair, though, this grasshopper definitely starts off as any other one—until, that is, Nick tells us:
These were just ordinary hoppers, but all a sooty black in color. Nick had wondered about them as he walked, without really thinking about them. Now, as he watched the black hopper that was nibbling at the wool of his sock with its fourway lip, he realized that they had all turned black from living in the burned-over land. He realized that the fire must have come the year before, but the grasshoppers were all black now. He wondered how long they would stay that way. (I.12)
Hm, interesting observation, don’t you think? Something has desolated the landscape and, even though it was a while ago, it still has an effect on the wildlife—maybe even a permanent one.
To put it bluntly, the metaphor here seems to be the war. “Ordinary hoppers,” i.e. ordinary people like Nick, have been affected, in some way reflecting the destruction of the landscape. And even though the destruction is over and has been for some time, he’s still manifesting its effects. And Nick has no idea if or when these effects will change.
But the episode with the grasshopper isn’t hopeless; after all, Nick tells the grasshopper to “Fly away somewhere” (I.14). The message here seems to be that life goes on. Sure, the grasshoppers are black, and they might be for a while, but that doesn’t stop them from being grasshoppers. In other words, if there is a way for the grasshopper to be free, then there is a way for Nick too.
Hemingway seems to be saying something about the way people wear their traumatic experiences. The grasshoppers literally “wear” what has happened to them by being the black color of soot. Nick doesn’t literally wear his experiences—as far as we can tell, he isn’t physically maimed—but he is carrying something that he can’t really speak about (many people still viewed shell shock and combat stress as a weakness that manly men needed to just “get over”). So he’s dealing with this thing that no one really wants to acknowledge. Therefore, we can’t see Nick’s trauma as clearly as we can the grasshoppers’, but that doesn’t mean it isn’t there.