In So Long, See You Tomorrow, the tenant farmer Clarence Smith doesn't just kill his near-neighbor Floyd Wilson. He also cuts off one of his ears and takes it away with him. Clarence kills Floyd out of revenge for Floyd's affair with his wife Fern. His whole life had been turned upside down by the affair, and he blamed Floyd for all his troubles. There was therefore a sense of inevitability about Clarence's murderous act.

But the question remains as to why Clarence felt the need to cut off one of Floyd's ears. The text of the story doesn't spell it out exactly, but there are hints, nonetheless. We are told, for example, that

In that pre-Freudian era people did not ask themselves what the ear might be a substitute for, but merely shuddered.

The clear implication here is that Floyd's ear is a substitute for his genitals. In his vast body of work, Freud often put forward a variety of possible substitutes for human genitalia, which were invariably imbued with deep symbolic significance. So in this case Floyd's ear could be seen, on a Freudian reading, as a symbolic substitute for his genitals.

Furthermore, the motive behind Clarence's cutting off of Floyd's ear could be seen as symbolizing a desire to emasculate his victim. Clarence doubtless felt emasculated himself when he discovered that Floyd was having an affair with his wife. In this act of revenge, therefore, he's seeking payback. Even though Clarence has already killed Floyd, he feels the need to go one stage further and emasculate him in a ritualistic act of mutilation.