Like other spiders, black widows bite for two reasons: to kill things to eat and to protect themselves. They catch flying insects in their webs and bite them so that they will stop fighting to get free. When people put their hands into this spider's web they might get bitten by mistake, but usually people get bitten when they squeeze a spider and the spider defends itself. Unfortunately, humans are very sensitive to the venom that the spider gives in its bite. The good thing is that widow spiders almost always run away if they can. If something big hits their web then they drop straight down to the ground and run away.