Messages from ‘The Metamorphosis’

The moral of Kafka’s short story ‘The Metamorphosis’ eluded me for some time. (See http://en.wikipedia.org/wiki/The_Metamorphosis for outline) About the terror and tragedy of a man morphing into a bug and being ostracised by others,what embedded messages are there?

I think it’s about one’s ability or limits of accepting change in oneself,
about others ability and limits to accept changes in ourselves,
about discrimination of one –
by oneself and others,
about speciesism.

As one morphs on, at what point does acceptance ends,
and at what point does rejection begins?