Don't Use That Toxic Crap in the first link!!!!!

It isn't necessary. Those chemicals are worse for you than the spiders. Go to your local feed and seed store or garden center and buy some d-limonene (orange oil - not the TKO stuff, but real orange oil) and pour a couple of ounces per gallon in a sprayer and spray the area. And you can also use diatomaceous earth (the organic gardening variety, not the pool filter type).

Dirt Doctor advice on black widow spider control. I have lots of wasps around here, so I don't have much of a spider problem.

SRS