Sadly, we have seen several dogs who have suffered spider bites (mostly Brown Recluse)--who ended up losing some or all of the affect limb. It's a long drawn out recovery--and often painful for the dog and owner. My Tina had a spider bite to her chest--took over 6 months to heal it up--but we did mange to heal it--no scar, full recovery. We were lucky.
Be sure to remove all trash, grass, leaves, etc. from around the foundation and walls of your home--no firewood stacks, lumber, rocks, etc. up next to your house. Get out that rake and keep those leaves from piling up next to you home. Be sure the underside of your home is sealed to keep out all type of critters. A few mothball thrown up under your home and up in your attic may also help keep spiders and other critters from settling up a winter home. Pick up and look up under all your dog house and SPRAY them with an insecticide to kill any adult of egg sacs. A little prevention may save you a whole lot of cure.
I have attached a very nice chart of USA spiders (sorry to all of our Canadian and other country friends--I don't know the spiders you have native to your locations!!)--please print off a copy and keep it for reference IF your dog or family should get bit by a spider. There are also a few first aid instructions for post-spider bite care.
Enjoy the beautiful Fall weather, and be safe. email@example.com