Tarantulas are part of the family Theraphosidae, which include the biggest spiders in the world, with body lengths of 3 inches to 4 inches. In addition to venom, tarantulas also use urticating hairs for defense, which are located on their backs and legs. When threatened, they push their bodies onto the predator to release the hairs, which liberate an irritating toxin. Species fond in the desert are often brown.
Members of the genus Latrodectus, black widows are toxic to humans, but rarely fatal. Dizziness, tachycardia, and muscle pain are common symptoms. Females have red markings on the abdomen and are bigger than males. They mate only once in their lifetime, retaining sperm to generate future eggs in special organs located in the abdomen.
With their long front legs and flat bodies, crab spiders are members of the family Thomisidae. They are able to move sideways and backward, and some species can present tan to white bodies, ideal to camouflage in the desert. Although the giant crab spider (Olios giganteus) is also found in deserts, this single species is part of the family Hetropodidae.
Wolf spiders are members of the family Lycosidae, featuring a dark brown body with light markings, which provides a camouflage cover in the desert ground. Wolf spiders are not toxic to humans, but the bite of some species can cause skin irritation. As active hunters, wolf spiders dig burrows on the ground, where they wait and capture insects that pass nearby.