I heard of someone who had a brown recluse bite
which actually causes the bone in his finger to
be dissolved and needed to be replaced. Spider
bites often result in digestive enzyme fluids
actually digesting the flesh where the bite is.
Sometimes the only treatmet is to cut around the
tissue before the juices can spread. I guess
spiders do not get heart burn or indigestion ??

i have heard that about "grand daddy long legs"
having poisonous venom, but jaws that are not
able to pirece human skin.

http://ohioline.osu.edu/hyg-fact/2000/2060.html

http://ohioline.osu.edu/hyg-fact/2000/2060B.html