If there's an image that summarises my idea of complete horror, this is it: a wolf spider carrying dozens of babies on her back. It's the only spider in the world that does this.
It's also the only spider that carriers her eggs in a round silken globe attached to her abdomen. After a gestation of 9 to 27 days -- it varies depending on the temperature -- the egg hatch and the infant spiders move onto the mother's back until they are old enough to hunt on their own.
These spiders are everywhere in the world, billions of individuals living in gardens everywhere. They are voracious predators, roaming the soil under the ground looking for other insects to eat. Sometimes, they wander into houses.
When I was living in Miami I had an encounter with one of these wolf spiders, one that was burned into my retina. I remember the hairy bastard walking down the rug of my bedroom, my girlfriend screaming, me using a shoe to kill it and then what I remember being two hundred thousand little spiders running everywhere. Then I screamed more than my girlfriend because I hate spiders like that. [Spirderzrule -- Thanks Karl!]
Another view of the abdomen plagued with spiderlings.
A wolf spider carrying her eggs in a silken globe on her abdomen. The only spider in the world to exhibit this eerily human-ish behaviour.