"But in severe cases, the bite may be painless at first, but over the next two to eight hours develop a sharp, deep pain followed by a burning feeling. The area around the bite reddens and spreads into a deep ulcer that can be as wide as 16 inches across and can take six to eight weeks to heal."
I knew someone who had a severe spider bite; she had to be hospitalized for it.
If bees did go extinct, we could always hire people to dress up as bees and pollinate flowers with tiny feather dusters. Sure it'd be more expensive, but there are also millions of idle teens.