A spider

I found out a strange spider in my garden with the size of 5 cm width, I didn't kill it with no harm. Because of some poisoning effect when I am hurt, I would often kill and destroy it immediately.
But the taught by Buddhism never permit to kill any living thing at all, following it, I pretend that I didn't come across with it.
No living thing on the Earth does not exist without any reason.
The possibility to appear here as an insect is very very few, it come here with conquering many hardships.
Probably the similarity of Genome of this insect must be over 95% with myself.
We have developed our frontal lobe, then are we the first on the Earth?
Do we have enough reason to destroy any other living ting because of our selfish convenience under the permission of God?
Such kind of doubt came up in my mind.
Spider never attack a man except the condition of being attacked.