What is sad about gregors metamorphosis and what is humorous?

Generally the family is rather repulsed by Gregor's transformation. This is sad as Gregor loses himself both physically and emotionally. Kafka was both subtle and ironic with his humor. Consider Gregor turning into a giant cockroach. The ironic and dark humor of this situation is not lost on the reader. Here the family's cherished son turns into a common pest both literally and figuratively.