The Black Widow isn't normally going to bite you, she hangs out upside down in her web, sits around there all day long, she's not aggressive, she is not going to jump out at you, as you are walking by. They don't hunt like that, they wait for prey to come to them. When a Black Widow bites you, you are going to feel a sharp pain initially, like a sting. Might swell up just a little bit, might be a little redness in the area, but for the most part you are not going to see much in your skin. You may also feel a fever come on or nausea, the fever nausea could last up to two days, and they are highly toxic. If you do have a very adverse reaction, then you will want to call a professional and get help immediately.