Dear Mr. Spider,
I am writing to express my sincere apologies for my deplorable behavior of last night. The altercation was entirely my fault. The whole unfortunate incident could have been avoided had I not carelessly--recklessly--failed to notice you and your lovely web hanging from the shower head. It must have been quite a shock for you, being awakened from your nap so rudely by my head crashing through your web. You were well within your rights to scamper across my face and down my back to escape my unwelcome attentions. I am certain that little detour down the crack of my rear was completely unintentional.
There was surely no cause for all that dancing and screaming. I am truly sorry to have interfered with your quiet enjoyment of the beautiful evening. I overreacted. It is perfectly understandable that you mistakenly ran up my leg to get out of that puddle. I am sorry I kicked so hard. I did not intend you any harm, and at least you did end up on that dry spot on the wall. You must have been terrified, which would account for your failure to depart through the window that I opened for you. I was only trying to nudge you in that direction; the loss of your leg was a tragic accident, for which I take full responsibility.
Had I been in complete possession of my ordinary self-control, I would have gently removed you from the shower and carried you outside. But it was rather late, and my judgment may have been a little impaired by my surprise at your unexpected appearance. And then there was the small matter of your unfortunate resemblance to the dreaded Brown Recluse. You do have the same long legs. And the same little brown body. And you are rather large for an arachnid. Most spiders of my acquaintance are slightly smaller than a frisbee. When you charged toward me like that, I failed to recognize the universal symbol for "Hi, let's be friends." I am afraid I mistook it for the universal symbol for "Hi, I am a huge, scary, poisonous spider and I'm going to bite you." Again, my fault entirely.
My behavior was inexcusable. I do not expect you to forgive me--what I did was unforgivable. But I do hope you will be able to find it in your heart to accept my most humble and sincere apologies for squishing you like that.
With deepest regrets,