I think Kafka purposely chose a cockroach. Can you think of anything more loathsome? The perfect thing to elicit horrific reactions. You may be shouting beetle but I still insist it was a cockroach.I won't attempt to do any more analysis than that as it's been done to death although I was surprised at how accepting Gregor was of his change. I will also say that I understood and liked this far more then The Trial.