Also sometimes referred to as sun spiders, are Arachnids known for their speed. They live in dry climates and feed on arthropods and other small animals. They can reach a speed of 10 miles per hour and grow to about 6 inches. Although their bite is extremely painful, they pose no threat to humans. Their powerful jaws, which can be up to a third of their body length, aids in killing and feeding on insects, rodents, lizards and small birds.