Answer:
At the start of the book, Gregor Samsa might have turned into such an insect but it's clear when you pass thru the entirety of the series that the rest of his won't alter. Whenever anything and someone is going via a transformation, there must be an abrupt difference not just in physical attributes as well as from within.
Gregor may also have altered but he somehow decided to work and provide the food and money he required for his relatives. He realised that his family had been able to fend for themselves in his death as an insect since they can no longer rely on him to continue providing their wants.
