I see this ending badly.
First let me say that I did find your story quite amusing.Uh yeah....agreed.
You're ordering spiders when you were told by your mother not to? So, you're going to hide them? What happens if your mother finds them? It will likely end badly for the spiders. Whether you like it or not, you live under your parents roof and part of that is respecting their decisions. Not only is it disrespectful to go against her wishes, but you are possibly endangering the lives of these tarantulas.
However, I do have to agree with Amoeba and Shell. It is your mother's home. She has the right to make the rules pertaining to what is and is not allowed in her home. As long as you live under her roof, you should respect her decisions.