Spiders have on this planet for 400 million years. They are predatory insects that eat other insects (even other spiders) and small animals. Most spiders are harmless to humans. The most deadly spiders are the black widow spider, the yellow spider, the hobo spider and the red legged spider. These spiders have enough poison, or venom, to kill with one bite. Spiders are able to control how much venom they inject into their prey. In face, can even bite without injecting any venom. This is called a dry bite.