I remember I was riding my motorcycle along the south-eastern US coast when I was hit in the chest by a stag beetle. I was doing about 75mph, and I thought I'd been shot, and I nearly crashed my bike. (I've been shot before, and I can tell you it's not pleasant.) I had no idea how big those things got. I was wearing a heavy leather jacket over a flannel shirt and undershirt, and I still wound up with a bone bruise.
When I lived in San Francisco, I had a friend who owned a South-American Brown Tarantula. This was a BIG spider with a leg-span of almost a foot. One day he noticed she wasn't eating, and had a large bulge between two of her legs. He was very worried about her, but didn't know where to take her. I mean, what vet treats spiders? Most of them just laughed at us. Finally, one suggested we take her to the Entomology department at Berkeley. So we called them and the fellow there said to bring her on down. So he looked at her and said she had a cyst, common to tarantulas. He drained it with a needle (that's when I discovered that tarantulas' have blue copper-based blood) and she seemed to perk up. Later that night when I called him he said that she ate all of her pinkies as was doing well. He still had her two years later when I moved from the Bay Area. (I have no idea how long tarantulas live.)